feeling like I cheated..:

So, I've been with my bf for 4 years now. I just recently got a new job. Now my SO and I aren't perfect but we would never cheat on each other as we've had it happen to us in previous relationships. To be clear(before I go on) I have not physically cheated. There's this guy at work, I think he's funny and maybe somewhat attractive(in a scruffy looking way) but I would not date him. Also because I have an SO. Anyway, I had a dream last night about him, and it was one of those dreams. I feel like I cheated.....has this happened to anyone else? I probably should not think much about it, but it kind of bothers me.