I (25F) found evidence that my fiance (26M) is on a dating site. I don't know how to feel or what to do.

My fiance, my boyfriend for a few years before we got engaged last year and I are getting married in June. We don't live together because he lives with his brother to help him pay rent and I have my own studio apartment nearby. It's been a big topic of contention lately but he keeps telling me he feels bad and can't just leave his brother with the two bedroom house he signed a new lease on last year. I've been staying with him a lot lately but stay home at least a night or two a week to be by myself.<br><br>We've had a few problems lately, but I've been really trying to do my part to fix them. I thought things were going a lot better, especially since he got a new job with better hours and is less tired on our weekends together. We got a lot of stuff done this weekend, I got all the invitations done and he got all of the RSVPs handled. So by the end of the night last night, I told him I was going home, I wanted to relax with my dog and get ready for the week. We ordered delivery for a late dinner and I was reading a book aloud to him as he played video games, and he had me pause so he could play a game without interference. I went and got another slice of pizza from the kitchen and wanted to come back to the living room (my brother has a large connected living room and dining room) and that's when I saw him on his phone. It was bright in the room and the screen on his phone was bright too so I saw it immediately. He was on a dating site and was currently chatting with a woman. It's the same dating site where we met, but where he's also met a lot of other women before we met (he was engaged to another woman before we met but they broke up and it was a messy breakup and he had a hard time getting over it and meeting other women). <br><br>I was in shock and didn't know what to do. I didn't want to give him a chance to do anything, to try and cover it up or delete anything. I quietly took the pizza and went back to my apartment. <br><br>I've been going back and forth about what to do. I have a wedding dress and I've ordered a custom veil. My parents have already paid for the venue and the caterer, so I'd have to pay that back if I called off the wedding. I'm also supposed to move in with him after we get married, but I just signed a new lease for my studio and the owner (my mom's cousin) said he'd love to have me for another year. I don't want to make my parents sad, but seeing that really took the wind out of me. I don't know what to feel, I'm mad at myself for not trying to figure out what was going on with him, but I'm also mad at him for being open on the app and hiding it when I saw him. I don't know if I should confront him about it or just end it right now. <br><br>What should I do?