God knows ahead of time if you're going to Heaven, right?

God does not want you to be burdened by sin, that's why he sent his only son. Once you get close to Jesus and have him in your heart, your sins are forgiven. Only one person was ever able to be the lowliest of humans and that was Christ himself, and that was because he was God in the flesh. You however are not to die for the sins of all humanity (as far as I know) an thus you don't need to burden yourself like you are. Perhaps it is in that way you are drifting from God, you are putting too much pressure on yourself and not accepting the grace he has given to you, kind of the other extreme that most people have. Listen to the voice, find your own path back to Him. Everyone gets second chances to be close to God, most ignore it however and laugh. Good luck to you