Hi -- I agree with alot of what H3rmit says. I've found that when a woman suspects something, generally, she's right! Call it women's intuition or whatever -- I don't know. But I don't think women dream these things up for fun cause it ISN'T fun -- it's miserable.
Chances are he's doing nothing. Try not to think about it. You'll screw up the relationship over nothing. When you begin to think like that, switch your mind to something else - pretty soon it will become habit.

And continue talking and being open & honest. I hope things work out. God bless and please take care. Hugs, Lee