I am going to agree with Windseeker as well! I am in a relationship that is exactly the same; my husband of 11 years has bipolar as well as ADD (apparently they are linked) and we have 4 children. We are an absolute mess and at this point I am not going to walk away; I have way too much at stake...but you don't have to go through this!! Let him go; as a very important lesson to learn about what to avoid in choosing your future spouse. That is what dating is all about; but I understand that it is not easy! I promise you though, you will fall in love again and hopefully with a person who is healthy and will be a good eternal companion.
This talk is very helpful:
Choosing and Being the Right Spouse - Ensign Sept. 2002 - ensign
Good luck!