Seeking expert counseling is a sign of strength. A personal relationship with a caring professional is proven clinically effective.
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What do you mean by "signs"?
If you ask hims outright, he will deny it, most likely, and then you will only establish that you don't trust him.
If he IS having an emotional affair, he will redouble your efforts to hide it from you.
Your best approach is to watch and see not for signs, but for evidence that there is a real person or persons involved in his life with which he is having such an affair.
Mentioning this to him may push the entire affair, if there is one, into a full-blown affair and you will regret having done this.
My advice to you is to give him the benefit of the doubt, be kind to him, and be watchful without acting as if he is already guilty.
If there is something going on you will find it.
I shall keep you in my prayers.
Elliottl, MAE, LPCC, NCC, CCMHC