Unloyal thoughts

I've been married to my husband for 7 years. Although we have only been together for 3 of those years. When I found out he was doing drugs, I lost all my sexual interest in him. Well he had a slip up about a month ago and now all I can think of is one of my exes so now I'm always wanting to have sex with my husband so I can be satisfied, but I'm still having these thoughts and not reaching satisfaction. I just think it's weird that before I had no desire and now I do, like have I lost feelings for my husband? I've never had thoughts of another man like I'm having now. I so badly want to follow through with it too. Because my husband has cheated on me and I felt cheated on and betrayed when he was doing drugs