How can i stop loving someone that i no is bad for me ?

i was with my ex for five months and me and him where like Pink and the brain we where so in sync we never argued . everyone thought that me and him where gonna last . He broke my heart the moment his friend texted me and told me he say my boyfriend with some other girl , so i texted my now ex and told him i wanted a break , he thought it was for the summer . he told me he loved me and then a week later i checked my facebook and he had just changed his status from me and him to him and his new girl .it broke my heart over and over again , i couldn't eat for a few weeks after wards and everyday is so hard because im thinking about him all the time . i feel like im lost inside the maze of my broken heart and im trying to find a way out . it feels like i no there's something missing and as hard as i tell myself that i don't need him and that time will fix my heart i still have that numb feeling , i blocked him from everything . i have those days where i feel like i can finally breath and that i can Finlay see the light , then something happen es to remind me of him and im back feeling like im in limbo . i wrote him a letter and one of my friends sent it to him . i feel like i cant love anyone else , im scared that i didn't stand up for what me and him had , im scared that i didn't no what to do . Hes been my world for five months and to be thrown away like a piece of gum just hurts .i got asked out on a date the other day and i dunno i feel really guilty in my stomic and i feel like i cant give anyone that emotional or physical connection . i dunno how to get over him ,