First time in intense pain

So I really fell in love with a person, i screwed up a lot of friendships in the process. He was a friend of my ex-boyfriend, but we had a fleeting thing and I really fell for him. He felt the same, but when the truth came out he (understandably) wanted to end it. But Ive never felt so devestated & lost in my entire life, the pain I feel is physical. I cant eat, sleep or think of anything else but him and the memories stir in my head. It seems so dramatic but I cannot switch it off. I know we cant explore it right now, but how the hell do I move on. How do I give up on the hope that something might happen?