HELP ME - do I have any chance?

So my ex dumped me 3 weeks ago. When I went to his house to get my stuff he told me, "I would take you back now, but I don't know if that would be good for us right now" an he said, "I just think we should be friends for awhile, and maybe more again later on" I spent that entire day at his house and we ended up having sex. A couple days later I went back to his house and knocked and rang the bell for an hour before realizing how crazy I was being. I apologized on Facebook but he was furious at me. He told me that I needed to learn to live without him because that was the only way we could be happy at this point and we needed to stop being in contact for awhile.
A few months before we broke up I started getting emotional because I discontinued a prescription drug that started making me feel sick. He freaked out at my being over-emotional and in stead of being there for me in my withdrawal he distanced himself. Then he started talking to an ex of his who literally ripped his heart out and stomped on it. It really hurt, and I made that clear. He started neglecting me, so whenever we were with friends he barely payed me any attention but messed around with other girls. I started getting jealous and he told me he was afraid I was going to go crazy. Then this girl came along, and she was like the perfect example of a girl who would be what he wanted. And I found out that he slept on a fold-out couch with her. I don't think he cheated. But it's still disrespectful. The problem is, I love this guy so much. And I think I destroyed any chances of getting him back.
Do I have a chance?
If so
Should I take him back if he asks?
And
When should I re-establish contact?