I think that it is first important to think about why you feel that he is cheating, confronting him right away is never a good idea (trust me from experience). You have know evidence or proof, just some suscpicion. Its hard I know, to not say anything, but the first thing they do is get defensive and you are looking at a hostile situation that you have nothing to back up your claim. I would just be "aware" and start to pay attention.
This is what I did and I am not saying at all its the right thing to do, just that it worked for me.
I started checking the cell phone bill. I looked for an abnrmal amount of calls or text messages t one number. I did find it and he was actually calling and texting it more than me, so I called it and blocked my number. I got a female and asked for my spouse by name just asking if he was there. She laughed and said no, he will be later, he is with his (not so nice name) wife. I asked who I was speaking with and if I could leave a message. She told me her name, I knew who she was and I said nevermind and hung up. I than called and got the actual texts sent from our provider. I than told a mutual best friend of ours who was more mine than his, a fellow military servicemember...seeing as we were all tecnically once in the Marines, he had my back too even if it was a short time I was in..like boot camp is it...lol. He confirmed the affairs...I then called my husband at work, asked him to come home and confronted him. He denied everything.
I stayed because it was all circumstantial really, we moved and years went by and I found pictures of him kissing her in an old box in our garage when he was deployed to Iraq so I sent them in his next care package sitting on the top so when he opened it that is what he saw. I already had full access to his email because he was trying to prove that he was faithful and I hadn't ever checked it so I did and he is a dummy and didn't delete the trash, just the sent and there were recent emails between the two and it wasn't very much in his favor. He admitted they were inappropriate and than he emailed her saying they can't talk anymore and blocked her. I checked and I called her command and asked her supervisor to ask her to leave us alone. He did.
I left him after that but he never did admit to that one. Another time I wasn't so nice and confronted him with a captain morgan bottle aimed at his head and told him to start talking and he admitted to six affairs and one my bff