I dont know why I cant move on from my ex

I dont know how to really go about this basically me and my ex broke up 5 months back she has moved on and doing good in the sense that she knows for sure she doesn't see me that way anymore. I am just afraid honestly I dont want to be that guy who can move on from their ex I dont really want to get stuck like this, but the problem is despite her flaws despite all her bad qualities I really cannot see anybody better. Its frustrating because its easy to say that there will be others out there but when you are not even able to find someone as good who you feel so at peace with its hard. I really dont know what to do right now I wish I could get some sort of clarity