My (f18) bf (m20) said he likes something about me because of another girl

What does it mean when your boyfriend brings up a girl he used to like TWICE during sexy time together? What does it mean when one of those times he tells you he likes something about you because of her? He basically compared me to her. He said the reason he likes when I wear these particular shorts I wear a lot is because she (that girl he used to like) wore the same. My mind just instantly floods to all the times he got so excited over my shorts, so excited it was almost kinda weird, because it’s just a pair of shorts. But it all started to make sense. He was like obsessed with those shorts when we first met and I never knew why until now. I remember he would have me send him lots of pictures wearing them. I wonder if he was imagining I was her when he saw those. I cannot get this out of my head. He also has like a particular “type” of girl he likes and I don’t fit that type and it bothers me even more that that girl fits his type. I’m almost sure that he really wanted to be with her and would rather be with her right now instead of with me. I feel like he settled for me. I think he misses her. I feel extremely jealous and I think about this every day. This happened several months ago. I still break down and cry about it like it happened yesterday. He’s been saying now that he didn’t mean it like that and he likes the shorts on me. He says she was just the reason he realized he liked those shorts. But he didn’t say that. If that’s the case then how does she have any relevancy to now, to me? It hurts me so much. He didn’t say he liked the shorts because they look good on me. He said he likes the shorts because it reminds him of another girl. He tries to assure me that the girl means nothing to him and he doesn’t care about her and he wants me and only me. How can I believe him?? Sorry I feel like this sounds stupid to outsiders. “Oh, it’s just some shorts, get over it.” Am I overreacting? just feel so unwanted and ugly and unlovable. I feel like I’m not good enough for anyone. I don’t feel special anymore. I don’t believe in love anymore. I feel betrayed. I feel worthless.

Tldr: my bf said during sexy time he likes my shorts because of a girl he liked in the past and it has destroyed my confidence.