How can i move on from my high school crush........?

i also regret that i wasnt more confident wiv guys when i started college at 16 cuz i neva really went out or even ever had a boy friend. when i started i just had a feeling that this guy was staring at me and smiling and i umed he liked me. he would help me in cl, talk to me during awkward moments but i was too shy to even spk cuz he was hot and i didnt have self-esteem at all about myself. when i see him in pictures with mates and girls and kissing the girls at parties i feel rejected and hurt. i dont know why. can u plz help me get over him?