moving on after cheating

I want to Move on after my fiancé cheated on me but it's so hard. He tells me it was just a physical thing and he did it because it was easy and threw herself at him. Whatever the thing is I'm trying to move forward with him and he's been doing everything I've asked from him but I'm still not satisfied. I wonder what I could have done different before even though I know it's not my fault. I'm emotionally exhausted and I just want to trust him again but my guard is up high. Our communication is better but I feel lost in this situation. **i understand people will be blunt with me in comments so I won't respond to it. if anyone has been in this situation I would like some advice or tips please**