How do I deal with heartache?

I'm 22 and lost my girlfriend of 2 and half years. She broke up with me at the start of April. Lately we have been talking as friends and I keep breaking down to her. I messed things up and regret it. This girl is the one for me. I've told her that but shes in a relationship with a guy 6000 miles away thats in the navy. She going to visit him this month in Hawaii where hes stationed and she told me she plans to go out there again in October. Hes too far away and she cant see it. I doubt its going to work since hes not coming home for 2 years. I miss her so much. I cleaned my house and found cards from her and all I do is think about her. When I do I get nausea and I feel sick. I've tried dating other girls and its worthless. I want her. Im still going to be her friends because she said that you never know. I do beleive that if its meant to be then I have nothing to worry about but this is the first time my heart has been broken this bad. How have you all dealt with the worst heartache?