Does it ever get better?

For context, I (24f) was cheated on by my at the time boyfriend (now fiancé 24m) 5 years ago. There were times I was confident that he cheated on me with others, but i couldn't prove it like I could this time. Well, after 5 years we've done A LOT of work to get over it. And I felt like I finally was over it about 2 years ago. So, I thought i fully trusted him again and we ended up having a baby. Postpartum has been extremely hard for me. I've had suicidal idealizations very strongly after not having them for a couple years. So I reached out in a local Facebook group for moms and met another mom who just gets it, we've become very good friends. Though, the weird thing is that her boyfriend is the ex of who my fiancé cheated on me with. As in, while he was cheating on me, this guy was still dating her. So, there were some harsh feelings at the beginning between my partner and my friends partner, but now everything is fine. The only thing that sucks, is since all 4 of us know who the girl i got cheated on with is, she gets brought up in conversations a lot. And unfortunately, it is bringing up bad memories from 5 years ago. Someone answer me honestly, does it truly get better? Or am I just going to have to feel like my trust will never be 100% again for the rest of my life? I don't think he's cheating now, and I really don't have any reason to believe he is. But becoming friends with this other couple is just bringing out old emotions that I thought had completely faded away.