AITA for getting with someone soon after a break-up

Me (F18) and my ex-boyfriend of 3 years (M18) split up after a very rocky relationship but we mostly ended on good terms and were planning on giving eachother’s stuff back very soon and “finalising” our break-up.

Two weeks after we broke up we still had not given our stuff back but he had made it very clear he did not want to get back with me, despite this (unbeknownst to me) he had not told any of his close friends we had split up yet.

Fast forward another few days and I decided to go to the club with a group of my close friends, for the second time in my life, baring in mind most of them go every week at least once. When I was there I met a boy who I had been texting since I broke up with my ex. One thing led to another and we made out on the dance floor.

My friends were all standing together with a group of my exes friends while this was happening and one of his friends recognised me and immediately thought that I was cheating on him.

He texted my ex while I was mid kiss and when I checked my phone later, he had blocked me on everything, except for Messenger

Last night he messaged me calling me a whore and saying he hates me so much because of this. I also want to add that the friend who saw me kissing a guy has cheated on his current girlfriend multiple times and my ex knew about them all and never told his girlfriend so he obviously has no respect for other people when it comes to cheating.

AITA?