Hi,
I know exactly where you're coming from; the pain, the confusion, the fear. I had my own bad break-up in Febuary and I took it much worse than my first, he left me for someone else so getting back together didn't remain a pipe dream for too long but I can remeber wishing he'd change his mind but being afraid that he would.
Its only recently that I haven't felt utterly weighed down by all of these feelings, they sadly only get easier to handle with time. I kept wondering where I could get this time, where could I buy it. It doesn't seem possible but somehow things realign. I started to see a therapist (I wasn't sleeping or eating for the first week and a half so it was pretty imperitive). I talked about my feelings ad nauseum with friends, I tried to stay busy and I joined eharmony. At first I wasn't anywhere near ready to be with anyone but it helped to know there were others out there looking for someone and slowly I've started communicating with them.
I really lost myself in my last relationship and so I thought I would take the time to get to know me. So yes I started therapy, I love dance so I started dancing and doing yoga again, and I've started exploring tantra for myself. Go out and do things just for you. Take a class in something, eat your favorite junkfood (a little), watch a T.V. sereies you've always wanted to see back to front. I made a list of the things I wanted from life and the person I wanted and I talked about that with close friends. Try to treat yourself with as much love and affection (with a little indulgence) that you would give to a lover.
At first I only had good hours, than good days, now I'm almost to whole weeks! It's always two steps forward one step back but slowly I've felt more in control of who I was and more confident that I deserve someone who will make me a priority in there life. Monday I made a post similar to yours, but that was a bad day. I worry though, because in September I'll have to start seeing him twice a week and that frightens me. I'm not sure how to handle that, or how to act....
One last thing, I started reading a book called "Looking for love in all the wrong places", it's about people who form unhealthy bonds. The person the author decribed at first seemed like my ex (kind of), but what was chilling was the person who would date that person was me! The feelings and thoughts the author described the lover having were the ones I'd been struggling with. It helped me grasp my feelings. (the book is a little dated).
I hope this helps a little, let me know how you're doing and what you're doing to keep busy. Support systems are key

....to quote Redgreen "I'll be pulling for you, we're all in this together"