Help, don't know what else to do

What do you do when you know your partner is faking? We've been together more then 14 years so I know him well enough to know, plus there are clear signs. When I call him out on it he gets angry and denies it. I've tried doing different things and even asking what would work better. It's been going on for a couple months now and it's killing me. Nothing like knowing you don't do it for your partner exp when your trying to have a better marriage.