First off, I'm sorry for the pain he is putting you through. I too suffer from bipolar and at times I get very self-centered and start to push people away because of various delusions. I can speak from experience that he's not going to change or get help until he sees the need or wants to get help. I didn't think anything was wrong with me and I refused to seek help until my wife (at the time we weren't married yet) gave me a "you're going to see a psychologist or I'm leaving" bit. So, I kind of feel for you "boyfriend" and I can understand what he is going through.

That being said, it is not fair to you and he has no right to be playing with your emotions like he is. He's doing it because he can see that he can do it because you're letting him. It's not fair that you love someone that is putting you through the ringer. However, I'm a firm believer that he won't change unless he wants to, and you running to him and caving to his ever need is no motive to change. He's stringing you along and you're allowing him to do just that. It's not healthy for you to be doing this to yourself. You're making yourself sick (ie the depression) in the process. You shouldn't give anyone that power over you.

It may not be the best for him that you walk away but it is in your best interest for you to walk away. You need to look after your own well being instead of his. You can't help him if he doesn't want your help. The fact that he called you over and you gave him sex and he ignored you again afterwards shows that he's just using you for his own self-gratification. It's not healthy that you're so freely giving yourself (both emotionally and physically) to this man that shows no respect towards you, let alone loves you. If he truly did love you he wouldn't be doing half of what he's doing to you, regardless if he's sick or not.

I can't tell you what to do, the choice is up to you in the end, but my advise would be to cut ties with him until he seeks out the help he needs. Best of luck and I wish you well. Please look after yourself.