Why can't I get rid of feelings for my ex?

You never really do. I still think about someone from 25 years ago. But that is harmless. Like the other day was watching a rerun of Seinfeld and remembered the time we were watching that on her parents couch and her dad caught me grabbing some of his daughters boob. Fun memory.

I was pretty devastated when we broke up. But eventually I grabbed other boobs and the memories tapered.

Eventually you move on. It sucks, but everyone that is happy has done it multiple times.

It’s normal to feel that way, so that’s the “why.” It hurts to lose people we care about, and I think it’s especially hard in circumstances where it doesn’t make a lot of sense, like the one you described. It’s hard to move on when the ending is confusing or doesn’t match the rest of the relationship- but you still do it the same way. Reflect on the good times, learn from the bad, lean on other people who care about you and start looking forward with your life and the things you want and eventually the intensity of that grief fades and you’ll find yourself ready to be in a relationship with someone new.

How long has it been? You gotta give it at least 6 months.
They say you never get over your last love until you meet your new love. Have you been going out, looking around for that new love??
You may never really get over her. I knew a girl 40 years ago and I still think about her.
You may have to give it a LOT more time!

Time will take care of that.