What can I do about a lack of proof?

Before I met my current girlfriend on the dating apps I went through a sleeping around phase but I didn't tell her. I first met a guy off Grindr about four months before we ever spoke. We went out and hooked up but I ended it when he wanted a serious relationship.

I got on the more reputable dating apps a month later and pursued both casual and long term relationships. I began messaging my girlfriend but I left out a lot of my past I wasn't proud of and I didn't tell her I was dating around. There was a guy on there that I hooked up with three times, the last being a few days after my first date with her. I stopped meeting other people but I kept Grindr and the other apps. When things were going rough in the relationship, I would send pictures on Grindr but went no further.

This year, my girlfriend started questioning my past more and I lied about it and trickled the truth. Almost all she got out of me was on my phone. Unfortunately I had long ago deleted the texts from those two guys like I did with my previous girlfriend who she knew about. She saw all the conversations on the apps though.

My current girlfriend is now thinking that those two men are more significant and that they overlapped with our relationship, and says she will leave if I don't tell the truth about it. She told me she knows I'm not cheating anymore but she thinks I'm lying about back then. I've given her full phone access, showed her messages with friends and where I stopped talking about sleeping around, and offered to have my friends vouch for me on this but she says this isn't enough.

I don't want to lose her and I don't want her to have to live with these serious doubts. Has anyone gone through something similar and gotten through it?