I don't feel okay right now

I'm dating my girlfriend for at least a year now and I'm her first bovfriend and apparentlv she's not a virgin and I did asked her that before when we started dating and I didn't asked how many before me but she said a story of 2 men so I thought I'm the third one, at first when she told me that I'm actually okav but days after days It's killing me because she's my first time even tho I had 2 girlfriends before her. Reasons that nothing happened with my exes is because I don't want to knocked somebody else plus I'm very young that time. So moving forward I told my girlfriend about these feelings and yeah she alwavs assure me but for me it's not really effective so what I did is to totally pay no mind attention about it as long as we are happy but I still I feel this feelings frequently but I love her so much so I disregard it everytime it always come back. Then fast forward right now we were happy until I logged into her account (we are ldr right now) because we are betting about she said something about me last 8 years ago back when we were high school classmates and after I won the bet we ended the call since its only her break and for some reason I want to know more about her since before we started dating we don't have any connections that time so we last saw each other when we are high schools and met again after college and that's where I found out that I'm not the third one through the chats with her ex best friend. don't know I feel hurt and these feeling that I felt before is much stronger. I'm not insecure about the boys she had sex with, I actually feel verv confident about myself. It's just I feel like what is mine was taken, my very trophy was soiled, the fact that is not just mine hurts me so much. Right now I haven't told her vet I still love her very much but I don't know what to do.