I (23F) have known my ex (23M) for 4 years now

I (23F) have known my ex (23M) for 4 years now. We became friends in 2020 and after a few months we caught feelings and decided to date. From March 2021 to May 2022 we were together, but it was super toxic. We argued all the time he’d verbally abuse me and some other stuff I don’t even wanna get into. In May 2022 we went no contact. Even though he treated me horribly I still missed him still loved him and lowkey hoped he’d come back so we could try again. But I never reached out.
In January 2023 he texted saying he wanted to talk. I responded (yeah I know, dumb) and next thing I know he’s outside my house begging me to come out. I’d already told him over text I didn’t wanna rekindle anything but seeing him there and hearing him say he missed me made me so happy. I asked if he’d dated anyone while we were apart. He said no. I didn’t date anyone either—just focused on work and school.
After that he kept pushing to show me he cared. Dates, trips, family events, posting me everywhere, being there whenever I needed him—it was all so sweet. We even started talking about marriage and a future together. But recently I found out he was with someone else the whole time we were broken up. Let’s call her E. He sent her money for Plan B in June 2022 and had multiple pregnancy scares with her. I always felt like he was hiding something but I ignored it because I loved him and wanted to be happy. He makes me so happy and I thought we had something special.
When I asked him about her he first said it was a one-time thing then admitted it lasted a while but was just a distraction because he was hurting over me. He won’t tell me when it started when it ended or who ended it—claims he doesn’t remember.
now I feel like I was just his backup after she broke his heart. I feel so stupid for even considering forgiving him especially when I know he’d never forgive me if it were reversed. I could maybe forgive him if he was honest, but he’s not. He won’t confirm timelines or give me the full truth. Like was he with multiple people? Is he hiding worse stuff? I suggested couples therapy but he shut it down even though he says he’ll do anything to make it work. Is that just another lie? Has everything been fake? Am I dumb? Can this even work?
People say guys cope differently but if you really love someone would you do this to them? Would you lie and deceive like that?
I know I’m young and there are so many people out there but I feel so stuck right now. I don’t know what to do.