Boyfriend with mental illness taking its toll..help?

It's very hard to be with someone that has mental illness, my mother was with someone like that and eventually after 4 years he committed suicide, and trust me it's been 4 hard years, argument all the time, i suggest you talk with him about it even that he may not handle it well so do it outside, he may say he will commit suicide or something, you can also talk with your family or psychologist about it, good luck.