Boy problem..PLEASE READ AND HELP?

so me and this kid went out for awhile he was my first everything he is a quite guy and we hungout like everyday went places with his family and all that cute stuff and so we decide to take a break because i lied about something before we were gong out and the next day he called me sayin how he wants to still wants to be with me and i told we could still talk and the next day his friend and him hungout with two girls and one of them i knew as a old friend and they drank and hooked up that night he called me and we talked on the phone like nothing happen he didnt tell me and when i asked he lied to me and the next day he told me "me and alana got drunk and hooked up.." i didnt reply "im sorry" i didnt reply "say something" i didnt reply he called me at 11 that night i ignored it and the girl messaged me and said sorry i didnt reply the next day in school he comes to my locker i just walked away..idk what to do him and her are having a thing now and its been three days after are break up wtf...please give me advice :(