I would ask him flat out whether he now feels that the marriage was a mistake and does he, in fact, want out. And when you do it tell him that you will agree to a divorce if that's what he really wants. Nineteen years' old is not too young to be a mature woman. You should make it clear that you will do anything you reasonably can to help him even if that includes separating.
Be prepared to listen with understanding to anyting whatever comes your way. I don't know what he means by "guilty" and I doubt he does either. Someone cannot be guilty of anything unless they do something to regret. Perhaps he feels that he wasn't honest with you, that is, that he loves you as a friend and lover but not as a wife. His "guilty act" was marrying you when he knew inside that it was not the right thing to do.
Your husband is young, perhaps too young and inexperienced to exist on his own outside his circle of family and friends. Maybe he got married because everyone "expected" him to after you had been going together for such a long time. ("It's time to get married, son.")
Offer him a way out without regret or recrimination. You didn't do anything. A marriage based on guilt can only lead to a sad and lonely life. An early separation will be embarrassing, but that is a small price to pay rather than spending you life in a bad marriage.
Good luck.