what should i do?

so there’s this guy i was talking to. we’ve talked romantically plenty of times before over the last 4 years. he liked me freshman year and i didn’t feel the same bc i got a bf. i liked him sophomore year and he had a gf. then i kinda forgot abt it last year and this year bc he was dating the same girl as he did sophomore year again but this time for longer. they broke up and as usual the first person he ran to was me and automatically i dropped everyone for him bc he’ll always be my #1. well we hung out outside of school for the first time and a few days after that he was weird and leaving me on read all of a sudden but still good. then he just stopped talking to me. and it’s a lot to explain but i feel like i just can’t let it go and need answers as to why he stopped. he said he’s over his ex and ik he’s talking to other girls on snap, so i don’t get it. when we hung out it went SOOOO well too. :/