Please help...husband cheating?

On the 18th I got a really bad gut feeling husband was cheating based on various subtle signs. I confronted him about it directly and he denied it. I tried hard to believe him, then he started being super nice to me every day after that. Like out of character nice. Today, I go to his email (which was open out in plain sight on our shared computer) and find several emails titled “Pineapples.” Full of the same girl’s photos. None of them are nude, but very suggestive. He said “his male friend sent them to him and she’s just some Instagram model” and he decided to email them to himself. But isn’t that a super unnecessary step if you have a phone with a password that I don’t know?!

Also. He can’t tell me the IG model’s name, and the pictures are low quality. And some of them are literally no makeup bathroom selfies in a tshirt, why would his friend send him those?! And guess when they started...the same exact day I accused him of cheating but had no evidence at the time. We have two baby boys, tomorrow is Thanksgiving, I cannot handle this 😭😭😭