Some of the things that help is always look for positives and keep the promises you make. This will be to start off with
I think you should set boundaries for yourself and be assertive of what you don’t like.
Set clear standards of action and be grateful and acceptable towards yourself.
Give yourself rewards for small victories.
Acknowledge your worth.
Do what fears you. Take risk.
For example I'm bad at math and so I do read biology everytime. So I started solving mathematics. When I reached upto 50problems in 1hour. There I found a satisfaction. And I congratulated my own self.
Another one, to overcome bodyshaming you can develop a habit of daily workouts. When your body become well shaped ,your confidence will be boosted by this .