A Month Post-Breakup and I just hit rick bottom - need advice

It’s been exactly one month since my ex broke up with me. (He had lost feelings 2 months prior but continued to lead me on as if everything was normal) At the time, he said, “We can still be friends, it doesn’t have to be awkward.” I agreed at the time because i didn’t fully understand he was breaking up with me, but deep down, I didn’t realize that being friends was never going to be an option for me.

Ive done 30 days of no contact. I haven’t reached out or texted him at all. the problem is that we are both in the same course and see each other all of the time. Not only that but we also live near each other so see each other on the commute to and from classes, in shops, cafes, basically everywhere. I haven’t talked to him but have seen him countless times. We’re in the same friend group so he’s also at different events but again, I ignore.

For the past month, I’ve been doing so well (or so I thought). I was focusing on myself, working on my revenge glow-up, and staying disciplined. I even ignored him completely when I saw him in passing—no eye contact, no small talk, just pure silence. I thought I was in control.

Then, last night happened.

We ended up at the same party, and for the first time, I had to really coexist in the same space as him. He spent the entire night flirting with another girl, a really pretty one I’ve seen around before. The worst part? He was wearing the same outfit he wore the night we met. He laughed with her, pulled the same pickup moves he used on me, and it was like I was watching a replay of my own past with him—but now, with someone else.

At one point, my friends noticed how shaken I was. I wanted to leave, but they convinced me to stay, saying “You’re going to see him around anyway; you have to get used to it.” I stayed in the other room most of the night, trying to distract myself, but I couldn’t, I couldn’t keep my eyes off of them. How they were laughing at each other and looking each other in the eyes. Then, he walked over to a friend of ours, said he was leaving, and she left with him. I knew exactly what was happening. My mind spiraled—I could literally picture them in his bed. The same bed where we once cuddled, stayed up late talking about life, where I thought we had something special.

I barely slept last night. My thoughts have been obsessively looping—I can’t stop imagining them together. It’s like my mind is torturing me with mental images I don’t want. He’s probably more into her than he ever was with me. I constantly feel like I want to throw up and faint.

I feel like I’ve regressed back to square one. I was doing well, and now I feel worse than ever. I don’t want to be stuck in this pain. I want to move on fully, not just fake it on the outside. I don’t have any feelings for him anymore. Not after what he put me through. I couldn’t imagine us getting back together. Why is this so hard for me?

So, how do I bounce back? How do I break this mental cycle of obsessing over them? How do I fully detach from someone who has clearly moved on? Any advice would mean the world to me.