This is a difficult problem, and you don't provide enough information to really offer a good view of the situation. You say she says she doesn't want you anymore. Why? Was it something you did? Was it just because of the fight? What was the fight about? You may not feel comfortable answering these questions online, and I don't blame you. Really, you should take this problem to a priest, minister, or therapist whom you trust and feel comfortable with. Seeking the opinions from older family memebers may also be a good idea.
All I can tell you is that it doesn't look good from where I'm sitting. You should not have cohabitated and had a child before marriage. Because now you don't really have a case. She is under no obligation to you whatsoever. You do have the right to see your child, and she appears to respect that. Aside from apologizing for anything wrong you may have done, and telling her that you love her and want to marry her, you may want to point out the child has the right to his parents, and to be raised in a loving household by his parents. If just for his or her sake, is it not worth trying to work this out? As I said, though, we are not really able to help you with this sort of problem online, and perhaps it is just as well.
I hope everything works out for you.