Awh honey, I know how you feel. I was with my boyfriend for 6 years.. we have a baby together. He was the only guy I had ever slept with. We were sopose to get married. Then we broke up, he was sleeping with someone else.. and I should have hated him.. but instead I didn't care I just wanted him back. I felt like I'd never be happy again. I tried dating other people and never once felt a simmer of what I felt with him.. and I hated it. I missed him every second of every day and eventually I tried to kill myself. .. It's weird what love does. I have a decent job, I'm in my last year of med school, I have a beautiful son, a good family, good friends, but i felt like the pain would never stop.
.. The thing is, it probably won't.. but everyday it will get a tiny tiny tiny ounce better. And probably for the first couple months pretty much unbearable.. but eventually you will get numb.
Keep your head up. Keep yourself busy with whatever you possibly can, even if your not enjoying yourself and just thinking about him. It's what you need the most. Keep yourself surrounded by people even if its the last thing you want.
... These are some really good books even if it sounds silly.. "It's called a breakup cause it's broken" and "He's just not that into you"