Let’s rephrase things. “If I’m an alcoholic, can I receive Communion?”
Well, obviously alcoholics are not barred from receiving Communion. Alcoholics who are no longer drinking would have no problem at all.
OTOH, if Bob has gotten blackout drunk every night this week, and he didn’t go to Confession about it on Saturday afternoon because he was still drinking – well, probably he shouldn’t receive Communion until he gets to Confession.
And obviously, if he’s drunk out of his skull on Sunday morning, he could still go to church (although he’d better get a ride if he goes, and it might be better for him to stay home and rest and dry out), but he probably shouldn’t try to receive Communion. He should wait until he’s back to himself, and properly disposed to receive. And he definitely shouldn’t receive under the form of wine, because that would just be asking for trouble, and wouldn’t be fair to Jesus.
But he should definitely try to go to Confession as soon as possible, and he should definitely get help to stop drinking!
OTOH, if he were on the point of death, Father wouldn’t hesitate to give him Communion viaticum. He might be careful to avoid the Host being thrown up, but it wouldn’t bar the man from receiving.
You could also get a situation where someone literally has no control over the situation, like if Bob had been dry for twenty years, and then was kidnapped by people who forced alcohol down his throat. Obviously in that case he would have an addiction and temptation problem as long as he was being forced to have alcohol. But it wouldn’t actually be his sin; it would be his kidnappers who were sinning.
If a person is fighting against an addiction, and trying to amend his life but often failing, that doesn’t mean that he should stop fighting, and act as if nothing were wrong. If it’s difficult to go to Confession before Mass so that you can receive Communion, that’s something to talk to Father about (or send him a letter, or whatever procedure you follow to get a message across).
There may even be situations where what would normally be “grave matter” would only count as a venial sin. Usually this is in situations where someone doesn’t have full volition, or when they were caught by surprise by a temptation and didn’t think about it. (And obviously, this is something a priest would be able to talk to you about.)
If worst comes to worst and you can’t get to Confession, you can just stay in your seat and make a “spiritual Communion” in your heart, because you can’t receive physically at that time. That’s what the saints have done, and that’s what you can do. You can even make a spiritual Communion when you can’t make it to Mass, or on days when Mass isn’t offered where you are.