Married woman infatuated with another man.. HELP!!!?

I have been with my husband for 8 years now. He's like my best friend and I love him very much. Of course there are things about him that I'm not crazy about but that's normal right? Well I met this other man who I absolutely can't stop thinking about. I feel so guilty about it even though I would never do anything with him. He's very attractive and very charming. If I was single he would be the exact kind of guy that I would be attracted to, the kind of guy that would be my type. My husband was never my "type" but I fell in love with his personality and for the man that he is. So then why after all these years am I even looking at anyone else the way that I would if I was single? Where did this even come from?? I feel like such a horrible person! I actually fantasize about this other man and I'm scared that something might happen that I'm going to regret. How do I stop thinking about him? A married woman should have no reason to think about another man. I can't help it though.. I know this sounds bad and I'm not a bad person and I do love my husband very much but for some reason this other man is like my dream guy that I have been looking for my entire life.. or at least when I was single. Ever since I met him I'm even less attracted to my husband and it just makes me want to cry because he's such a good person, but I can't help being so attracted to this other man and thinking about wanting to get to know him better. What should I do? I never thought I would ever be in a situation like this.