hatingtoberight I think you have certainly done the right thing by confronting your husband and nipping this in the bud before anything may or may not have had a chance to develop.
My ex dh had an affair with a woman who right from the start my instincts told me there was something not right about her. I even said to ex dh at the time that she was a potential home wrecker and he agreed.
She always flirted with him and siezed her chance when I was out of town one night. From then on he would take his mobile into the bath with him claiming he was playing games on it.
I never had reason to make me suspicious until one evening when he was going to do a job for her after he had finished work but came home and had a bath and put on his best aftershave first.
I later checked his phone and found loads of text messages that he had sent to her and the rest is history. We're obviously divorced now, he's married to her and I've re-married and she's now the bain of my life(thats another story!!) ex and I have 2 dc's together so un-fortunately I still have to see her ugly smug face every week.
Looking back I probably, like you, could've nipped it in the bud but I chose to do and say nothing.
I know your dh hasn't actually cheated on you, but with women like that they have a way of getting under men's skin so if you hadn't done anything about it, it would only have been a matter of time.
Well done to you for being strong and getting through this.