now in my 30s, i say be upfront about your gut feeling and bring it up, in a non accusatory fashion. it could clear the air or make your gut feeling worse (which usually means move on (to me) or something is happening that you are not fully aware about(could be nothing could be something etc)). though for most of my life, i sat with the bad feelings in my stomach instead. and I'm glad that i don't any more. it's also important to note that traumas from our past can also cause our gut to go crazy, so it's important not to jump to conclusions, and to communicate clearly and respectfully and kindly. good luck!

He wouldn't bone your friend to intentionally hurt you. He'd bone your friend because it feels good. Then, he'd probably hope you don't find out about it. Bottom line: Your gut is right, so dump him and move on.

Trust your gut. But talk to him and see how he reacts about if he's noticed how she's acting. I had my suspicious about my best friend of 33 years through a few boyfriends but blew it off thinking she would never. None of them ever would touch her but sure enough she was trying.

My gut has never been wrong about infidelity in my relationships. If behavior appears incongruent and inappropriate to what it should be, it's because it is. The warning signs we try to justify away always look blatantly obvious to us in hindsight, and this looks like an obvious one. Confront him directly in a moment where you are emotionally calm and secure. Most people don't lie well when confronted and emotions aren't heightened. And then you can judge from there if he wants to do what's necessary to save the relationship with you.

Go with your gut feeling