1. Go to the movies alone. Pick a film you want to see and get a ticket. Get popcorn if you want and sit and enjoy the movie. Another time go out to eat alone at a restaurant that you are interested in. Do things like this regularly. It helps you be comfortable with making decisions and taking charge and it helps you be comfortable in your own skin regardless of who is around and who is looking.
This forces you to make hard decisions (the movie, the restaurant, etc.) and stick with them. It forces you to be comfortable in public alone where you don’t have friends to take the focus of others around you. You are there alone and everyone sees you and if they don’t like it they can suck a nut.
2. Wear your best underwear to work. It sounds silly but a friend gave me this advice years ago when I was having a bit of a confidence crisis about my looks and my clothes. I wore my best matching knickers and bra set under my regular work clothes and I felt fucking amazing! It’s amazing how a good tit day can boost your confidence.