My ex cheated on me with my cousin.

Crazy story.. In November 2018 I met my ex. I fell for her hard! I had a deeper infatuation with her than I have with any other girl. We dated for 9 months and during that time, we had a pretty decent relationship. Then one night she calls me at 3 in the morning crying and told me she got drunk the night before and had sex with my cousin. I was appalled, but loving her as much as I did (or being infatuated) I was willing to forgive it. I tell her that I want to continue our relationship. She wouldn't allow it. So we ended our relationship after 9 months but continued having sex for another 9 or so months. After the break up, we still acted like a couple, but that slowly went away. On June 1st 2021, we had sex for the last time. We both agreed that it would be our last time. I still had feelings for her at this time and we agreed to remain friends. We continued talking as friends and met up every now and again. Then one day I flipped out over text and finally told her how I felt about her cheating on me with my cousin. She told me she did that because she wanted our relationship to end, but didn't want to break up with me, so she did something she thought unforgivable. Then I started feeling resentment towards her, so I decided I needed to stop talking to her. But it ain't that simple. So I was going to do something to make her block me on everything. She would have to hate me before I was out of her life. I told her that after we broke up. Anyway, I made up a lie that I got another girl pregnant and was going to have a baby.. I kept this lie going for quite a while.. Long enough for the baby to be born and start walking. Then one day not long ago, I decided to call her and tell her the truth. Sure enough, she blocked me on everything and told me not to contact her again. And now, I am still infatuated with her to the point where if the opportunity arose, I would take her back. I know, I'm crazy! But at the same time, I feel alot of resentment towards her and want her to suffer. I also partially blame myself for the relationship ending in the first place. I need to get over this! I deserve better! I should have been over this long ago!. So that's my story.. Thoughts, comments, questions??