How to actually move on?

I don’t know why I feel so anxious whenever I think that my ex (and first love) will get an other partner. I know I’d be so happy for him but something about it still hurts me, I know deep down a part of me still isn’t healed from wounds that were created which makes me have trouble moving on. It’s almost a year now since he broke up with me, and he didn’t treat me the way I deserved either. But I don’t know why I still can’t move on fully? I got in a relationship 6 months after him and I got cheated on, i moved on fast and became a good version of myself. But I still want to understand why I can’t get over my first love, I have so many hobbies i do so often, friends and family i talk to about it, and I even got in so many advanced classes. I want to become the best version of myself, and im taking a step at a time. My most important and biggest step is moving on from my first love- the guy that broke my heart after my birthday. Please give me advice,🤍🙏
How to actually move on?
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