Should I be mad about this?

My boyfriend has always told me that he’s always considered me his first love. Today I finally asked him about his ex which I’ve never done. I asked if she was his first love and she said yes. That kind of hurt me because he’s always told me that I was his first love. So I asked him I’m your second love and he’s like I guess sure. This bothered me because a year after we were together, I caught him sending his ex old

Memories of them on Snapchat. Of them kissing. So I asked him about it too and he said well idk why I did that I guess it was just lust… and that made me even more mad because he admitted to lusting other girls while being with me 😭 him doing that was 4 years ago but it still irks me and pisses me off. However him referring to her as his first love pisses me off even more because I always thought I was because he would always call me that. Hes my first love. Idk, I just want to break up with him over this because I feel like I’ve been living a lie. Feelings could also strong because of my period. Any advice appreciated 🩷