Boyfriend admitted he doesn’t know if he’s moved on from his “first love”

I’m 20F and he’s 19M. I’ll refer to him as C. We’ve only been together for 2 months. Yesterday, C wanted to show me something in his photo gallery and I saw nudes of some girl. I asked about them and he just casually said they’re from M. M is a girl he talks about a lot, even on our first or second date he told me about her. I asked him about the nudes and he said he just kept them all these years, though he no longer masturbates to them. He acted like it was a very normal “guy” thing to do, but I thought it was disrespectful to me and the girl that he kept her nudes, and that it should be the decent thing to delete them. I didn’t want to be controlling, but I felt really insecure and uncomfortable so I asked him to delete the nudes. He did it without hesitation, though I don’t know if he will recover them from the “recently deleted” folder. I want to trust that he won’t do that.

For context, C and M met when they were 13 or 14. She’s the first girl he loved and also his first kiss. They were both going through family issues at the time so they bonded over it and hung out everyday. M was sexually abused by her father and stepfather since she was a young child, so C was there for her and helped her through everything. According to C, she was the popular girl at their school and all the guys wanted to be with her. He’s described her as “perfect,” “beautiful,” “hot” and so on when talking about her. She treated C “like a brother,” so they never dated, though they did have mutual feelings for each other at one point. He told me he was young and deeply in love with her, and what they had was special and something he’ll never forget. Eventually, she moved to another country and he tried to move on from her. He dated many girls throughout the years, but admitted he was always looking for her in these girls and still pining after her for many years. When he was 18, he reached out to her again and they caught up and talked as friends. He realized they’re living vastly different lives now and that he’s “no longer in love with her,” but simply loves and cares about her as a person. I believe they’re still in contact now because he told me he got drunk with his friend one time and he texted M. Even his friend asked if he’s still in love with her, and said he shouldn’t be with me if he hasn’t moved on from her.

I told him I felt really insecure because he talks about her all the time. I feel like he hasn’t moved on from her. He admitted that he doesn’t know if he’s moved on and he “doesn’t want to know.” I think he’s in denial and just scared to admit that he still loves her and hasn’t moved on from her. I feel very hurt. I feel like I’ve been strung along our whole relationship even if he didn’t do it intentionally, and I will always come in second to her. I’m always comparing myself to her and feeling less than her. I don’t know what to do. I don’t want to be constantly trying to live up to her and always wondering in the back of my mind if he loves me more than her. Please help, any advice would be greatly appreciated.

TL;DR: saw nudes of a girl on BF’s phone, asked about them and he said they’re from “M,” a girl he constantly talks about and refers to as his “first love.” Asked if he’s moved on from her and he said he’s not sure and he doesn’t want to know