Am I doing the wrong thing?

So this is a very complicated question and I'll go into more detail privately if anyone is willing to listen and give genuine advice. But really short my girlfriend(f28) cheated on me(m25) over two years ago. It was a very messy and complicated situation then and she probably didn't think anything of it as we weren't really dating in her head. She told me we were. We stopped talking for a while after that. We got back together afterwards and recently things have changed for the better. But I still can't ever get that feeling like she's cheating again or that I shouldn't ever have tried forgiving her for it. And I'm afraid I won't ever really get past it and trust completely. Am I wrong for just letting it continue for the time being? For not being able to make a decision? And I wrong for dragging it out when it might be we get better and just end up hurting us both more the longer it goes on for? Like I said there's a lot more detail and I'll gladly get into privately with someone if they feel like they can really help. Thanks all. I needed to put this down and get it out of my head.