Obsession

I have never been diagnosed with OCD, but I have many traits of it. My question is- what is the best way to get over an obsession? I'm not sure i have experienced this before, but I am totally obsessing about a guy I work with. I think about him non stop all day everyday. We did hook up, but I obsessed so much about spending time with him, I think I freaked him out. The worst part is, I'm married. I've never cheated on my husband in 10 years. I feel so guilty, yet I can't stop thinking about this guy. I want to see him again, but I don't think he will give me the time of day. I have to get over this. It isn't good. How do I replace this obsession?

Having an obsession as a result of OCD is very different than being romantically preoccupied with someone, which can also be called an obsession. It's easy to get yourself confused.
However, at the risk of sounding like an asshole, I will provide you with some suggestions. You really need to think about the reason(s) why you cheated on your husband after all of this time & why you aren't sending these energies his way. It seems as if something has changed, in which case, it's not you that you need to work on changing-- It is your relationship with your husband. It would be wise to strengthen your relationship with him because, there is a saying, "If you have what you want, there's no reason to look somewhere else for it". If it is due to a sexual addiction, personality disorder, etc. then perhaps therapy would be a good course of action.
Hopefully you can eliminate your lingering thoughts about this guy. He sounds like he only wanted a one night stand anyway. Be well.