Find a support group for people who are in relationships with those who have bi-polar disorder and do your research so that you know what you’re dealing with in the relationship.
Also, if he won’t get a vasectomy, and you’re having sex with him and you have a child because of failed birth control, YOU should consider having your tubes tied so that you don’t put any more kids in this situation.
I’m sorry this is difficult for you, but the job you now face is to make sure it doesn’t get any more difficult and to try and make your child’s life the best possible one.