I want to have sex with someone other than my boyfriend?

I've been with my boyfriend for two and a half years and I really do love him. He loves me and he's so good to me but we're long distance and it's really hard. Recently I've started wanting to sleep with someone I work with. I don't have any real feelings for this guy but something about him turns me on so much I can hardly stand it. I want grab him by the collar and just throw him down and do him. I've tried to ignore these feelings because even if I do have a tiny itty bitty crush on him i'd never want to be in a relationship with him and it's not risk losing my amazing boyfriend over. I just feel like since I haven't seen my boyfriend in over a month and I have these intense flirtations going on with this other guy it's driving me nuts. I feel like I'm going to burst if we don't do it soon. He knows I have a boyfriend and he just recently found out how serious we are so he's kind of pulled away from me lately and that is driving me even more crazy. I feel horrible but I've never wanted to have sex with someone this badly, I just want to do it once and then forget about it. Am I horrible girlfriend? What should I do?