How to bounce back after past memoried have been triggered?

I am in need of support because I am currently experiencing intense anxiety and flashbacks over memories and it is really affecting me mentally. For context, a few days ago, my friends and I have been talking about our days in college and the topic of my ex came up. The conversation carried on to the things he has done, and how I felt that my budding friendship with one of the girls has been ruined. During the conversation, I wasn’t too affected as everyone including myself was certain that I had already moved on and I was sure that I was until I experienced an intense anxiety attack after they left. I had flashbacks of the things he’s done and of my mental state years ago. These went on for days coupled with anxiety attacks and thoughts of self-harm. My thoughts are filled with his lies, regrets about the friendship, shame, and self-doubt. My self-esteem has dropped since then. This came as a complete shock as I was so sure that I had already moved on and that my self-esteem was stable. Every time I get flashbacks about it, I keep crying, would feel like fainting, and would drink at times. I can’t bring myself to get mad at my friends or blame them because it wasn’t their intention to hurt me and it’s not their fault. A bit of context about my past relationship- It was my first serious relationship with a guy that I intended to go long term with. He tried hard to get my attention at first but when I agreed to be his girlfriend, his efforts died down. He would later lie to me about certain things especially about other girls which would make me feel inadequate as I would constantly feel like I was the only one putting the effort in the relationship. He is aware of my life long struggle with depression, social anxiety, and trust issues so his actions came as a surprise. One lie would be him having feelings for one of the girls in my class who I had a budding friendship with. This turned into a mess and I avoided her not because of anger that my ex liked her but because the drama made me feel like she hated me which triggered my anxious feelings about being liked. He would also lie about his past with his ex and would make comments about girls while putting me aside. I later found out that he did all this to punish me for getting attention from other guys (who I do not entertain) and that he was jealous. He claims that he doesn’t actually like those girls but wanted to hurt me by using them. This upset me and completely shattered my mental health and made me doubt who I am as a person. Throughout out relationship, some of my friends would blame me for his actions. This is another trigger for my anxiety and I spent months trying to get away from all the stress. I felt completely unloved and played and it was an immature mistake to have stayed longer than i could deal with. After the breakup, things were going great for me and found myself in a lot of success throughout my life and I managed to build myself up but the sudden reminder of this part of my life is making me feel like I was the same person almost five years ago which is giving me a lot of shame as I can’t change the past. What I have shared about my past may not seem much or too “traumatic” for some people but at that time, It was a big thing for me as It was my first time experiencing strong love for someone and I was a lot immature then. I was 18-20 that time and I am currently 23. I want to move past this and live normally again. I’m sorry for the long post, thank you so much for your feedback and have a nice day/night.