Boyfriend went behind my back with texting app

So my boyfriend (of 4 years) started getting messages from a number, it was obviously a texting app. None of what they were telling him was true, at all. These are the screenshots.

There were red flags this whole time, not very many people would have that picture. So .... It was him. I looked at his purchase history and hes downloaded 3 different texting apps. Somebody please tell me what to do.