how to move on from grieving!

I'm in so much pain after this breakup I don't know how to move on and be happy. All I want to do is cry and cry. I can't sleep or eat. He's got a new girl after a month and blocked me. He came back and hung out with me just to leave again and tell me he doesn't want me. Then he had sex with me last Tuesday and has now blocked me. I wish this wall just a dream. Everything is falling apart and I feel like I wasted 3 years. I just want the pain to go away. I just want to be okay and speed up this process. I just don't know how. This is the worst break up yet.