Hun, here is my point of view. Take it or leave it as is.
I've spent a good deal of my life dealing with people like this, both in my own personal relationships, and in my friends. I've watched as people have pitied the person they where with, to the point that even KNOWING that there was always that doubt, always that what if of their partner going and fucking someone else. ( Sorry for being blunt ) They stayed it through until said partner TOSSED them aside when another piece of *** came along that they wanted more. I've had people threaten to KILL themselves if I didn't stay with them, and one who tried to. He never succeeded. I am great full for that. But none the less if you know your not going to be happy with him, and that what your feeling for him is no longer love but pity instead. My advice is to let him go, gently if you wish.
If he decides to toss back pills, that is his choice, and if he is doing that rather then killing himself, off, at least he is showing some smarts. I know I am probably coming off as rather harsh, and I am not trying to, but when I am ill I don't... filter my thoughts well.
The point here is are you happy?
In your current situation?
Can you see yourself doing this everyday?
Do you WANT to do this everyday?
My last relationship ate me up to almost a husk, because my HUSBAND went off to fuck his ex. I tried reasoning it out, and I tried staying. ..and once he found something he wanted more. I was told with no doubt that he wanted a divorce. Didn't even fucking care.
So what choice will eventually make YOU happy?
This in the end comes down to you, not him.
His life is his own, distinctly and what HE chooses to do with it, is what he will do. Regardless of what you say or do, or choose.
It's up to you babe.
Make your choice, and be happy.
(whatever way you choose )