Building confidence

I barely had any confidence before last this relationship that I recently just ended. I have zero now after being in a bad relationship. Anyone have any advice on how to build confidence? I wanna be able to make friends, I have crippling anxiety so its hard to make friends anyways. I wanna be able to walk in a room and not be thinking about what everyone thinks of me. I wanna get out of this shell. If never felt this low in my life and really struggling. Any advice is greatly appreciated 💜