boyfriend of 2.5 years left

hi guys, i dated this boy for nearly 3 years. i was sure that he was the one. it was like something out of a fairytale. however, recently he stopped prioritizing me and would ditch me to go hang out with his friends, didn’t seem like he wanted to hang out with me, etc. he started coming up with all of these problems that i was doing, such as not texting him back fast enough and he came out and said he didn’t like one of my instagram posts because i was in a bikini, etc. so really easy things to fix and obviously i fixed them all immediately because i value his feelings and i’m not one to give up on people. i started trying even harder for him and it seems like everything i tried only pushed him farther away and he was almost getting mad at me when i would fix one of the issues we had, like he was looking for an excuse to leave me. long story short, he ended up breaking up with me with the excuse that he needed to “find himself” and because he “lost a piece of himself”. he did it very nicely, told me to keep his clothes and keep using his music app “until the day i die”. he was giving me really mixed signals telling me he “didn’t want to break up with me and he still loves me but he feels like he has to”. then i found out that he had been hanging out with this girl that i had been suspicious about at her house for HOURS in the months leading up to the breakup. i know because her ex boyfriend reached out and talked about how they had been hanging out and he gave me her address and it matched up with where his location had been showing for the past few months. he had been telling me it was his “weed dealers house”.. which i was obviously incredibly suspicious about 🙄. i confronted him about it and he swears it was only one time and gave me his word that nothing happened between them and that he just “needed another perspective” for what was going on in our relationship. i know it was more than once but i don’t know how to feel. how can you just leave someone like that after 2.5 years? i keep holding onto hope that we will be able to work things out because of the way he handled the breakup and how he told me he doesn’t want to leave and that he still loves me. at the same time, i know he was at that girls house and regardless of whether or not they did anything, he lied about it. i guess i just need someone to talk some sense into me because i’m having a really hard time letting this go because i have always been too committed to making things work and i truly believed he was the one for me. any advice or support would be appreciated, i’ve been feeling super alone since he left <3