Could you please tell me what's wrong with me?

The title poses a rhetorical question, and honestly, I feel like the biggest idiot sandwich ever. I’m a 21-year-old woman dating a wonderful 22-year-old man who has been the best thing in my life lately. Despite this, my life has a pretty dark past. My last three boyfriends cheated on me consecutively, and I stayed with them each time, only to be hurt again. One of my exes even cheated on my birthday, using the money I gave him for our electric bill to go to a strip club. My most recent breakup was about six months ago. Things went downhill when I refused to move in with him because I believed I shouldn’t have to relocate for someone to be loyal. We argued over minor issues that, in hindsight, were completely irrelevant. Ironically, we broke up on the very day I was supposed to move in with him. Nevertheless, we parted on good terms, promising to stay friends. We’ve known each other since elementary school and share a group of friends. Since then, I haven't truly healed. I thought I was doing okay, managing to push thoughts of my ex out of my mind by reminding myself of who he really was and how he made me feel—repeatedly. When I first met my current boyfriend, I was not looking for a new romance. I signed up for Tinder just out of boredom. We matched, he messaged me, and though I almost didn’t reply, his opening line was too amusing to ignore. I shared my Snapchat with him, and after a few days of chatting, I forgot about him. My demanding job as a handyman occasionally involves working 24-hour shifts with no sleep and tight deadlines. One night, I saw he had sent me multiple snaps, so I suggested we switch to texting. After that, we met up about a week later and instantly clicked. Fast forward to two months ago, I discovered I was pregnant. After much heartbreak, my boyfriend and I made the incredibly tough decision not to continue with the pregnancy. Since then, I haven’t been myself. He’s been there for me through every appointment, holding my hand while I faced the worst moments and caring for me when I was overwhelmed. I’d like to mention my ex again. Even after everything, I maintained a friendship with him because we have mutual friends and can’t avoid seeing each other. Recently, after he celebrated his birthday, I asked my boyfriend if it was okay for me to attend a party hosted by my ex. He surprisingly said yes, so I went. I brought some vodka, although I don’t typically drink much. The party was small, and I felt pretty comfortable, greeting my ex's mom with a hug. My ex hugged me, too, but it didn’t feel significant. We started chatting, and his mom encouraged me to take a shot with her. I have a limit of three drinks because I’m a lightweight. I had one shot but felt fine until another friend’s dad offered me a shot—he poured it directly into my mouth without a glass, and it was definitely a double. Soon after, my ex noticed I was struggling to stand and pulled me into another room for a chat. I kept the door open, trying to be cautious. He expressed gratitude for my presence and mentioned that it meant a lot to him. I asked about his new girlfriend, who he said couldn't attend. Out of nowhere, he offered me water, but I shrugged it off and asked for another shot instead. As I went to grab my drink, he pulled me back and kissed me. I was too shocked to respond. To clarify, I don’t drive at all—I'm not responsible enough for it. I was waiting for a family member to pick me up after their shift. In a panic, I broke away from him and ran to the bathroom to collect my thoughts, only to find him waiting with another shot outside afterward. In my anxiety, I took it, attempting to escape by stepping out for a cigarette, even though I don’t usually smoke. It calmed my nerves but left me feeling guilty for putting myself in that situation. When I went back inside, I found my ex again, and a moment of comfort led to me crying uncontrollably as he consoled me, wiping my tears away and encouraging me to breathe. Even though I hadn't mentioned my recent abortion to him, I couldn’t hold back my tears as memories flooded back. Despite the pain he caused me in the past, I felt a sense of security in his arms that I don’t experience with my current boyfriend. I found solace in a moment of weakness and gave in to a kiss from my ex. Instantly regretting it, I jumped up, dressed, and fled outside without shoes or a jacket. It was freezing, and I sat in a bush, sobbing until I felt ready to return. When I finally went back inside, I took another shot, feeling a strong urge to escape from my situation. My current boyfriend treats me incredibly well, but I struggle with self-worth, convinced I don't deserve him. It’s been four days since that night, and I haven’t talked much with him, but he knows something’s off. I plan to tell him face-to-face about what happened, but I’m terrified. Having endured betrayals myself, I never imagined inflicting such pain on someone else. I understand how selfish it is not to give someone the choice to forgive. Withholding this truth for three days weighs heavily on me, and I fear the hurt it will cause him. I aim to deliver my confession in person, but I'm unsure how to articulate it. I’ve realized I’ve become someone I despised—a cheater. I’m writing this to urge anyone reading not to make the same mistakes I did. Once betrayal occurs, it’s best to walk away immediately. I feel a heavy burden to bear, and if my boyfriend chooses to leave me, that’s something I'll have to accept. I intend to work on myself and grow from this experience. I truly hope I still have the chance for redemption.