What you need to do, is inform someone around him, his doctor, family members, friends, school counsellors (I'm just listing examples, no idea if he's a studen or whatever), someone who's close to him, anyone. Then you take a step back and close the door.
If he's gonna do it, then he's gonna do it. It has nothing to do with you and whatever feelings you may have for him. If he doesn't do it, then what he DID do, is put YOU through emotional stress that in the end is damaging to your own mental health. Whether you love him or not is not the factor that should decide what to do from now on. Your love is NOT what he needs, what he needs is help from professionals. The best thing you can do for both of you is to delegate the responsibility for his mental health to someone else, and walk away. It may sound awful, but it's the goddamned truth.