Hello Sister ... i can't help but remember one of your previous posts, it might have been your first post, and how it revealed your insecurity and lack of trust regarding your spouse. I think this particular situation is rooted in that same confusion.
Have you asked your husband is he cheating? Did he say no? Why don't you believe him? Has he done things in the past that has made it impossible to trust him? This is about your trusting him and not the fact that his "man toy" feels different. Sister, after doing most anything consistently for 12 years, momentum will wane. It doesn't mean he's cheating.
Maybe he is cheating. Maybe you have reason to be insecure, but you really must discuss this with him. No one else can possibly provide these answers to you. Only he can, and if you don't believe his responses, then you have a totally different problem, one greater than is your husband cheating or not. Understand Sister, if you don't trust him, it makes no difference if he is cheating or not.
It appears, from the outside looking in, that you are making yourself crazy. You've mentioned nothing above that is hard, concrete evidence that your husband has been unfaithful. You've only shared a few of the things you've "reasoned" inside yourself, that make you feel this way. Do you know that we have the ability to believe whatever we want to believe, even if there is absolutely no truth to it, or evidence to support it?
You obviously love your husband, want to be with him, and want to trust him. You've said that he loves you and has put up with your issues for all these years (like you've put up with his) ... yet you continue to imagine that things are happening ... with no evidence at all (or none you've shared here).
Only the two of you know what is really going on. If you are justified in these fears, and can never trust him again, perhaps you should let go and find some peace for yourself. On the other hand, if you are creating problems where there really aren't any, then perhaps you should focus and embrace what you have, before you push him into the arms of another.
Destee