How do you know if your husband is cheating especially if he is super smart about it?

I swear he is cheating. We never have sex anymore, but yet he still shaves his man goods. We don't go out together on dates, he isn't involved with myself or the children. He is always working! He tells me that if we ever split up he'd move on within two weeks. He constantly is looking at porn. And numerous times when i call him throughout the day he doesnt answer and then a couple times i would hear a girl talking in the backround... when i ask him who he is with he freaks out and says no one that im crazy. whats up? i need a guys honest and thoughtful input.