Should I confront or let it go?

About a year ago my boyfriend of 5 years befriended this other girl on Facebook who lived about 3 hours away from us. They started liking and commenting on all of each other’s stuff and he hearted her pictures rhen teied to hide the fact he hearted them from me by undoing it. They even shared a few things to each other and went back in forth in the comments. Well I kept noticing that she would text him while we were hanging out and he went on about how “weird” she was. Something didn’t feel right to me and I went through his messages with her. I know I shouldn’t have done that but I did, and I found out they were telling each other private, personal things about each other, she called him cute and he told her she’s beautiful. He even told her about our relationship problems. I confronted him and he swore he would delete her, he said they were just friends. Well he “deleted” her but I went back to his Facebook messages to find out he was still talking to her but had her on secret so I wouldnt see it. I confronted him again and he deleted her for real this time.

Well that girl has a boyfriend now and they Haven’t been Facebook or Instagram friends ever cents. I haven’t checked his messages again but I trusted him. I was going through my boyfriends Instagram and saw a page he followed about scenery/photography and I love pages like that so I clicked on it wanting to follow it. Come to find out it’s based around the same town that that girl lives in and almost all of the people who follow that page also follow her Instagram so I’m pretty sure it’s her page for photography. I noticed that my boyfriend liked several pictures from that page even after he claimed to have deleted her completely and that page liked some of my boyfriends selfies. Should I confront him or just let it go?