Sometimes it helps to be angry at the person. It's not a long-term solution, but one that may work in the short-term. If I offend anyone by this advice, I apologize, I am merely offering something that has worked for me in the past, and I would prefer that the OP be "unhealthily" angry at her ex than suicidal and hurt herself.
So try it. Think about how messed up it is that he left like that. Call him names in your head. Get a photo of him and draw devil horns on him. Tell yourself he sucks and you are so GLAD to be rid of him. I know it will feel wrong at first, because you love him, but anger is a very powerful emotion, and often will override sadness. Listen to angry songs by angry girls. Think about how your own mother or father (or whoever has loved you in the past besides him) would feel towards your ex if they knew he was driving you to suicide. They would be pretty pissed at him. So focus on the bad he has done to you, and (this is important) make sure you get in touch with some of those friends that you have been neglecting. There is nothing like an all-out ex-bashing between girlfriends. I am sure that at least one of them has bad stories about an ex of hers, and you two can commiserate. Then, by the time the anger wears off and the hurt comes back (unfortunately it probably eventually will), then you will have friends already nearby to help you through and do the real emotional work.
Look, the thing is, no matter what happened between you two, even if you think you did something wrong, NO ONE deserves to be driven to suicide because another person has decided not to be with them. Don't let him do that to you! Say no to him and no to his rejection. Switch it around. YOU can reject HIM. Why not? If he doesn't want to be with you then why sit around and glorify his memory? There will be plenty of time after the dust has settled and you are in a more confident state of mind to look at things objectively. Right now you have got to get MAD.
I think I am on the brink of losing my own relationship, and trust me, if it doesn't work out, this is the tactic I will use to get over it, initially. I hope it works for both of us. Good luck.