I still think that if Oliver actually cheated on her, Carrie would very strongly hint at that. The only reason why she might not allude to him cheating on her is that she’s scared people will remind her of how they began their relationship. She was very aware of the optics back then, which is why for years she kept playing with their official timeline until it seemed like they hadn’t cheated on their respective partners. But again, if he had cheated I still think we’d know by now, via “subtle“ IG stories/inspirational quotes.