Messy coworker breakup....any advice would be appreciated?

I'm a eighteen year old girl who is a full time student in university and works part time like many students. About six months ago I began dating a coworker. Things were fantastic at first. He was the sweetest most amazing guy and I thought like any girl that I was blessed to have found him! After around 3 months of dating things really started to change fast and for the worst...first of all he started to get really physical in our relationship...I was very clear to him that I wasn't ready for what he was trying to do and well...you can imagine how frustrated and upset he got at me over time with this. He also began to hang around this other girl at our job who was 3 yrs older than him and 4 yrs older than me quite intensely after getting frustrated with me a few times...as a result out relationship just weakened and weakened until I got fed up....trying to talk to him about the other girl and all the problems in our relationship was horrible and it led to a terribly messy breakup. We have been broken up now for just over a month and things are still incredibly awkward at work. He stares at me constantly when he is working at the same time as me, and has gone out of his way to make working their intolerable at times to say the least. At the time of the break up I told him that I didn't want things to be awkward seeing as we still had to work together...he later sent me an email saying he didn't think we should ever speak at work because it would quote "hurt us more in the end." Im trying so hard to forget about him and our brief 4 month relationship but seeing him all the time at work makes it next to impossible. Quitting or transferring is not an option, and in all fairness I have worked their way longer than him and have a higher position as a supervisor. It was a terrible breakup but I don't hate him. I want to move on and he is making it very difficult in many ways. I know many people say don't ever date a coworker but I broke that rule and now regret it. I was going to try to talk to him about it once but after the email, I cant even bare thinking of attempting it. The other girl by the way, hates me, tells other workers that its no lose because I was never good enough for the guy anyways, and she even spreads nicknames about me like "virgin mary" because I wouldn't be sexually active...how she knows all this information about my relationship I imagine she only gathers from speaking to my ex...whenever I see him or her at work I feel sick and I have not spoken to my ex or her since the breakup yet I continue to get the horrible glares from both of them and my ex still strives to make me jealous in many ways...any advice would be appreciated but please be serious. Thanks.