Trouble in paradise 🙄

I recently found out a few months ago that my fiancé had an encounter with an ex.. long story short what i was told was that he ran into her at the gym and they were catching up and one thing led to another they were in her car and he received oral sex and stopped her because he knew he was wrong. He has no contact with her no social media no number nothing (I checked) and we moved away from that area. I found out about this at the gynecologist (you know what i mean) when I confronted him he just lied and lied like I didn’t have proof 🙄 until I finally forced him to tell the truth but anyways we have moved on from this months later I find it hard to move on. We were fighting and stressed we just had a baby at the time he was a few months old. So it was alot going on im not justifying his actions he was wrong but I do believe it was an honest mistake I forgive him but I can’t forget. I get angry all over again sometimes songs and movies about cheating piss me off.. This man is my best friend the love of my life but I don’t trust him anymore. I don’t want to leave but We aren’t the same I don’t see him the same. Was I wrong for forgiving him? What do i do? Advice please