working with my ex...cant get over him

Hi. my boyfriend broke up with me 2 months ago and i just cannot get over him at all. i cry almost everyday, have lost interest in going out with my friends and cant sleep properly. the thing is my ex and i work together, pretty closely. he actually sits 2 seats away from me. seeing him every day kills me. he wants to be like my best friend, constantly coming to my desk to talk to me, wanting to spend lunchhour together everyday. i actually went along with this for a while, which i know was a bad idea but i just missed him so much and loved being in his company again and spending time with him. ive since told him that this needs to stop and that we shudnt be spending so much time alone together as if nothing has changed. he wasnt very happy about it but i think he knows it was for the best and so it has stopped. it seems to have helped me a little but not a lot. i find myself getting really upset in work and several colleagues have spoke to me and told me theyre worried about me. he seems to be having no problems moving on with his life and gettin on with things. he doesnt seem to be uspet. i actually dont like being off work at weekends or holidays because i dont get to see him and i really look forward to going back again. i know it shouldnt be like that. i have spoke to my manager about being transferred and she said if thats what i really want then she will try and arrange it. but she has asked me to give it another month first and see how i feel about it then. i dont really want to leave because i love my job and i love the people i work with, i have some very good friends there. people keep telling me i would be foolish to leave and jeapordise my career over him because hes not worth that. i dont really want it to have to come to this but i feel like the only way i will get over him is to be away from him completely. i feel like my life is just a mess at the minute. sorry to go on so long, just feel completley lost and dont know what to do