Can a person with Mortal sin on his conscience receive Holy Communion without confession?

 
Q:
I have a mortal Sin on my conscience but trying my hardest to stop the sin, I need Christ in the Eucharist to help me defeat it. Can I receive the Holy Communion without going to Confession?
 
A:
To understand the Eucharist, Mortal Sin and its consequence better, let us first look at the Catechism of the Catholic Church:
The Lord addresses an invitation to us, urging us to receive him in the sacrament of the Eucharist: “Truly, I say to you, unless you eat the flesh of the Son of man and drink his blood, you have no life in you.”¹ To respond to this invitation we must prepare ourselves for so great and so holy a moment. St. Paul urges us to examine our conscience: “Whoever, therefore, eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of profaning the body and blood of the Lord. Let a man examine himself, and so eat of the bread and drink of the cup. For anyone who eats and drinks without discerning the body eats and drinks judgment upon himself.”² Anyone conscious of a grave sin must receive the sacrament of reconciliation before coming to Communion. (CCC 1384-1385)
 
The Catechism of the Catholic Church goes further to explain Mortal Sin in greater detail:
For a sin to be mortal, three conditions must together be met: “Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent.” Grave matter is specified by the Ten Commandments, corresponding to the answer of Jesus to the rich young man: “Do not kill, Do not commit adultery, Do not steal, Do not bear false witness, Do not defraud, Honor your father and your mother.”³ The gravity of sins is more or less great: murder is graver than theft. One must also take into account who is wronged: violence against parents is in itself graver than violence against a stranger.  Mortal sin requires full knowledge and complete consent. It presupposes knowledge of the sinful character of the act, of its opposition to God’s law. It also implies a consent sufficiently deliberate to be a personal choice. Feigned ignorance and hardness of heart⁴ do not diminish, but rather increase, the voluntary character of a sin. Unintentional ignorance can diminish or even remove the imputability of a grave offense. But no one is deemed to be ignorant of the principles of the moral law, which are written in the conscience of every man. The promptings of feelings and passions can also diminish the voluntary and free character of the offense, as can external pressures or pathological disorders. Sin committed through malice, by deliberate choice of evil, is the gravest. Mortal sin is a radical possibility of human freedom, as is love itself. It results in the loss of charity and the privation of sanctifying grace, that is, of the state of grace. If it is not redeemed by repentance and God’s forgiveness, it causes exclusion from Christ’s kingdom and the eternal death of hell, for our freedom has the power to make choices for ever, with no turning back. However, although we can judge that an act is in itself a grave offense, we must entrust judgment of persons to the justice and mercy of God. One commits venial sin when, in a less serious matter, he does not observe the standard prescribed by the moral law, or when he disobeys the moral law in a grave matter, but without full knowledge or without complete consent. (CCC 1857-1862)
 
From these, we can understand that for a Sin to be considered mortal, the three conditions underlined above must be met (Grave matter, committed with full knowledge and deliberate consent). If you are actively and sincerely trying your hardest to stop this sin as you’ve said, the sin would lack deliberate consent and would not be considered Mortal Sin, in which case, the Holy Communion will definitely arm you to fight against it. But, if your sin meets the three conditions, it is mortal sin; you must first go to Confession to attain state of grace to receive the Holy Communion.
The Code of Canon Law elaborates on receiving the Holy Communion with Mortal Sin on one’s conscience:
A person who is conscious of grave sin is not to celebrate Mass or receive the body of the Lord without previous sacramental confession unless there is a grave reason and there is no opportunity to confess; in this case the person is to remember the obligation to make an act of perfect contrition which includes the resolution of confessing as soon as possible. (CIC 916)
 
My advice to you is to go to Confession as soon as possible when you have mortal sin on your conscience to attain a state of grace. While in a state of grace, I will advise receiving the Eucharist as often as possible; the Eucharist will help you tremendously in the struggle to defeat sin. As my final words, I’ll leave you with a quote from the Catechism of the Catholic Church:
“By the same charity that it enkindles in us, the Eucharist preserves us from future mortal sins. The more we share the life of Christ and progress in his friendship, the more difficult it is to break away from him by mortal sin” (CCC 1395).
God Bless you
 
 
 
¹  John 6:53-58:

53. Jesus replied to them: In all truth I tell you, if you do not eat the flesh of the Son of man and drink his blood, you have no life in you.
54. Anyone who does eat my flesh and drink my blood has eternal life, and I shall raise that person up on the last day.
55. For my flesh is real food and my blood is real drink.
56. Whoever eats my flesh and drinks my blood lives in me and I live in that person.
57. As the living Father sent me and I draw life from the Father, so whoever eats me will also draw life from me.
58. This is the bread which has come down from heaven; it is not like the bread our ancestors ate: they are dead, but anyone who eats this bread will live forever. (New Jerusalem Bible)

² 1 Corinthians, 11:26-32

26. Whenever you eat this bread, then, and drink this cup, you are proclaiming the Lord’s death until he comes.
27. Therefore anyone who eats the bread or drinks the cup of the Lord unworthily is answerable for the body and blood of the Lord.
28. Everyone is to examine himself and only then eat of the bread or drink from the cup;
29. because a person who eats and drinks without recognising the body is eating and drinking his own condemnation.
30. That is why many of you are weak and ill and a good number have died.
31. If we were critical of ourselves we would not be condemned,
32. but when we are judged by the Lord, we are corrected by the Lord to save us from being condemned along with the world.” (New Jerusalem Bible)

 
³ Mark 10:19:

19. You know the commandments: You shall not kill; You shall not commit adultery; You shall not steal; You shall not give false witness; You shall not defraud; Honour your father and mother. (New Jerusalem Bible)

⁴ Mark 3:5-6; Luke 16:19-31.
Mark 3:5-6

5. Then he looked angrily round at them, grieved to find them so obstinate, and said to the man, ‘Stretch out your hand.’ He stretched it out and his hand was restored.
6. The Pharisees went out and began at once to plot with the Herodians against him, discussing how to destroy him.(New Jerusalem Bible)

Luke 16:19-31

19. ‘There was a rich man who used to dress in purple and fine linen and feast magnificently every day.
20. And at his gate there used to lie a poor man called Lazarus, covered with sores,
21. who longed to fill himself with what fell from the rich man’s table. Even dogs came and licked his sores.
22. Now it happened that the poor man died and was carried away by the angels into Abraham’s embrace. The rich man also died and was buried.
23. ‘In his torment in Hades he looked up and saw Abraham a long way off with Lazarus in his embrace.
24. So he cried out, “Father Abraham, pity me and send Lazarus to dip the tip of his finger in water and cool my tongue, for I am in agony in these flames.”
25. Abraham said, “My son, remember that during your life you had your fill of good things, just as Lazarus his fill of bad. Now he is being comforted here while you are in agony.
26. But that is not all: between us and you a great gulf has been fixed, to prevent those who want to cross from our side to yours or from your side to ours.”
27. ‘So he said, “Father, I beg you then to send Lazarus to my father’s house,
28. since I have five brothers, to give them warning so that they do not come to this place of torment too.”
29. Abraham said, “They have Moses and the prophets, let them listen to them.”
30. The rich man replied, “Ah no, father Abraham, but if someone comes to them from the dead, they will repent.”
31. Then Abraham said to him, “If they will not listen either to Moses or to the prophets, they will not be convinced even if someone should rise from the dead.” (New Jerusalem Bible)