This relationship is unhealthy but I can't leave...?

Alright, boyfriend and I have been dating for nine months, both just graduated from high school. He has depression and social anxiety... I am basically his purpose in life. He has threatened to kill himself many times, and I am always the one thing holding him back. I'm the only thing that makes him happy. He claims he's alright and this isn't true, but I really don't believe it. He refuses to see a psychiatrist. We've been having problems for months now... I am not attentive enough, am too independent, I'm unsure about the future and my feelings are shaky... lately he has been critical of my weight (I'm 5' and 102 lbs, not overweight), he refuses to put his arm around me if he thinks I'm too squishy... I just feel very pressured. He also freaks out because I won't have with him because I want to save myself until marriage. In spite of all the issues, I promised him I would give him at least until I got into college before I broke up with him if I ever did.