How do I leave a toxic relationship where he is very suicidal or puts himself off to be as so. Yet he’s done this with every girl he’s ever liked just because either they didn’t work out or they just didn’t like him back.?

I’m not sure what to do anymore because I care about him and his well being but the way he acts and puts off to be is as he might try to commit suicide and my girlfriend told me to leave and some nice women on here have told me to leave too I just don’t know how to do it