@Anonymous Being cheated on is awful, I am so sorry you’re going through this!!!
I am going to give you the advice that I wish I had when I first suspected cheating in my past relationships, because I think it’s what motivated me the most to do what I needed to do for myself. There’s a fear side of our body and then there’s intuition. The fear is always significantly louder, so you have to sit with that fear without doing anything about it, without answering any of the what ifs or questions that are coming up. Once the fear isn’t as strong, you’ll hear your intuition more. It will be, “I don’t know exactly what happened in that situation and I will never know. Maybe it’s worse or better than I am imagining, but I can’t ever know that, and need to accept that. With how the relationship is right now, and how it has been, do I feel loved, appreciated, and are my needs being met? Is this the relationship what I want for the rest of my life? Does this relationship provide me with the stability and trust I need to feel safe in the relationship?” Fear may pop up again, but your intuition will sound like radical acceptance of the truth, and it will feel comforting, even if you have zero evidence or proof, you will know what the best path is for you, and what will make you feel more peace, even if you know what you need to do sounds challenging and really really tough. There will be less blame on either party, and more needs focused motivation. It may be a “I’ll stick this out for a few months, but if things don’t improve, I’m done,” or maybe you already feel done, or maybe you’ll want to work it out.
Do this with all of his behavior, not just the behavior that is suspect of cheating, but all your experiences together. I think you’ll find your answer there.