What should I do?

I know I shouldn’t have done this... but I looked through my boyfriends text messages and I saw that he’s still entertaining other females. Like, he meets up with them, speaks on the phone with them until he falls asleep, he doesn’t tell them he has a girlfriend, they send ‘x’ to eachother, they facetime... and god knows what else to be honest. And seeing that just really upset me cos I literally explained to him why I have trust issues yesterday and he said to me that I shouldn’t worry about the girls because they’re just friends and that’s it. But from what I’ve seen, it’s obvious that they aren’t just friends. Or the females obviously don’t know it. One of them has called my boyfriend about 7 times today and he keeps ignoring the call. Idk if it’s cos i was with him or not. But ugh I really don’t know what to do. Like, I know it’s not acceptable to look through someone’s phone. I know it’s invasion of his privacy. But I just wanted to trust him fully without something in my head telling me to stop being naive...

Since I looked through his phone, I’ve just been less talkative around him. He’s asked me what’s wrong with me and I said ‘who knows🤔’. I just don’t know how to tell him. Has anyone else gone through this? Please give me advice on what I should do/ how I should explain what i saw