Life changing news

So. I have been with my S.O for 9 years, ttc for just over 4 years. About six years ago we had an argument because there was a weird text on his phone. He claimed it was because of a porn site he was on, and I chose to let it go. I’ve known him for 15 years and we’ve always had such a close relationship. At the time I told him, I don’t care about porn, but I’m not cool with the person to person stuff online... for me it just feels too much like cheating. Fast forward to five days ago, when I confronted him (not the first time I’ve asked) about his shady behavior on his phone. Turns out he’s been messaging girls on Craigslist, as he puts it “jackoff material” and “looking at what people are into”. Not the whole time, but off and on... like an addiction he would tell himself to stop and then let time go by, then do it again. He swears nothing more happened and I do believe it. My problem is, this feels like such a betrayal of my trust. It doesn’t matter his intention, I told him how I felt. Now I’m not sure if I can ever trust him again. I feel like he had so many chances to fess up, and I also feel like he made my life decisions for me... getting engaged, ttc... I’m not confident that the news would have ended the relationship but I deserved the chance to decide for myself. How would you feel? What would you do? I want this back but I’m so afraid that I’ll never be able to let it go. I used to think we were such a perfect couple. 😔