I can tell you for sure that you should not marry him - he has already weakened you tremendously by divesting you of your main support system - your social and family life. This is really bad - you need to get out and deal with the left-over attachment to him once you are out and free. You can get therapy to explore why you are still attached to him, etc. - you do not need to be in a relationship to get therapy for what brought you to the relationship.

If you carry to term and deliver the baby, you will need to file for support from the guy and be prepared to have him co-parent if he wants to, because it will be within his legal right to co-parent, regardless of your marital status. He might not want to, but if he does want to, you will have to contend with his presence in your child's life. I do not know whether you are considering terminating the pregnancy, so just stating the obvious to make sure you understand that one of the consequences of deciding to carry the pregnancy to term is having the guy affect your life for the next two decades.