I know exactly how you feel, also. It actually took me almost 2 years to get over someone I had dated. I had never had that problem before I was always perfectly fine with breaking up with others but one person I just lost it. I couldn't eat or sleep or do anything. I tried of course to get it off my mind acting like I didnt care, going out with friends, flirting with other people...but as soon as I went home and sat in my room by myself I lost it. It was horrible. See my ex started dating one of my friends. The thing is though I was the one who had broken it off that's why it was so weird that I couldnt get over it. I was in love though. In a way I still am but the good thing is after a little time goes by, the pain will subside. It's completely normal to be jealous of who he's dating as long as it doesnt get into stalking or anything. The point is let yourself heal by itself...that's what I did wrong...I tried to hard to ignore it but of course it didnt go away. I'm not saying stop your life to worry about his but I am saying that if you give yourself time to cry and time to think about everything and don't hold your feelings or your emotions against yourself, it will be much easier to heal yourself. If it's meant to be it will be.