I want to move on quickly from my ex-boyfriend who broke up with me 3 weeks ago
Why would you want to move on quickly?
I'm his ex-girlfriend, I don't want to be with him again
I agree that people move on on their own pace, so you moving on quickly from your ex is a normal behavior. If you are having issues trying to move on from him, try to maybe go to dating apps and see if you can find someone new to date.
I don't want to do that
I respect that decision. You can do whatever feels right.