<human>: Condense the text into a few key points

Background information- I've been seeing this guy for about 2 years now, and I feel like we fight a lot (maybe every  few weeks or so.) These aren't big fights, and they aren't over anything big. Usually, he gets insecure and then kind of takes it out on me.

He then says things like "you should just go find someone better" or "there's something wrong with me," which forces me to be the one to subdue his problems, when he's the one that first created them.
 
He used this "mental illness" as an excuse for his actions, which I don't think is fair. I know mental illnesses are a serious problem, but he has never been diagnosed, so I am really skeptical. I've had friends with depression and bi-polar disorder, so I know how hard it is, but he's never been tested. I've been telling him for a few months to go see a professional, but he has yet to do so.
 
I just don't know what to do, and I'm at my wits end. I love him a lot, but I'm just so tired of dealing with this. Any help is appreciated!
<bot>: SO uses mental illness (undiagnosed) as excuse for actions, and I don't feel like that's fair.