confused after breakup

just broke up with my long term gf a month ago and have been feeling really weird lately. we dated for 5 years and things were kinda toxic so i knew it was the right thing to do but now im lost. ive started hanging out with some friends from grad school again who i used to hook up with, nothing serious, just for fun ya know? and last night one of them asked me out on a date and we ended up at her place and stuff happened. its not like before though, she seemed so into it and it felt different. now im scared that im some sorta cheater or asshole but also worried i might actually be falling for someone else after only a week. what do u guys think? am i the asshole here? is this normal right after ending something major? im really confused about how i feel and dont wanna mess up again. any advice appreciated.