My exboyfriend is bipolar

So here's the deal... Me and my ex have been broken up for about two months and he's been with his new girlfriend that same amount of time, before we broke up they were something like friends he was talking to her about our relationship, then the week we broke up he brought her to the apartment that we live in to be frank it was the exact day we broke up. Three days later they had sex, and then started dating and the same week they fell in love, and he allowed her to move in a week later when she was kicked out of her aunt's home for not following their rules (mind you she is 18, he's 21 and I'm 22). Well I've been with him 2 1/2 years we'e talked about marriage, kids, what we were going to do after we finished school, but then he all of a sudden changed his major, his attitude toward me has changed especially when she's around he's really hostile but when we are at home alone he wants to have conversations that are civilized and jokes here and there but I'm so tired of the wishy washy attitude even though I know he is bipolar and is not taking his medication. They're moving out at the end of the month but I'm still dealing with the situation the best way I can and try to continue being that friend that I have been for 3 1/2 years. What should I do? And how should I react to his rushed realtionship with her or what should I think of it? Do I let him go? Or do I hold on to him? I'm really confused about this.... Help please

goodness what a ??? i'm not sure what to suggest...her living there..u living there...him living there..this is all, imho, out of whack to begin with. jme, but i would not want to stay with a person who is hot and cold about me, or someone else, regardless of his dx. plus he's not on meds so that just puts another factor in the mix. if i were u, i'd just get on with my own life and try to find mr. right if you're looking for mr. right. there's too much that needs fixing with this scenario, jme. good luck with your decision whatever it is. sorry i couldn't be more help.

Thanks, and believe me I've already signed the proper forms to put him out and she has 14 days he has 30 since his name is on the lease with mine. But it feels like an entity in my house when she's here and when she's not it's so peaceful that's how I know for sure that she is trouble. But I appreciate your input, and I don't even allow him to use his disorder as an excuse these days.

atta' girl, miss keke!!!!