That is really difficult. It's hard to lose someone who is a giant source of support in your life, even if it wasn't working out romantically. It makes me think a lot of what drew you guys together was that he was acting somewhat as a therapist for you and that's the kind of support you need right now.

It also highlights why you need new sources of support and companionship in your life, and to maintain the bonds you already have with others. Find close friends who understand. Learn how to deal with these things without having to ultimately rely on others. That doesn't mean you have to do it alone, but it does mean that you have to be self-motivated about your own health and ultimately take responsibility for it.

I guess the major point I want to make is that he is not the only one who can help you with these problems. He's just the only person who has been able to and who you've asked for help. There are others; it's just a matter of finding and reaching out to them.