How do you get back to yourself after toxic relationships?

I’m currently trying to detach myself from my toxic ex-boyfriend/baby daddy. We were dating for four years and I’ve completely lost who I am to the point where I can’t even look at the mirror and recognize myself or find any trickle of self identity. How do you get back to your old self your new self but feeling like yourself again. I remember before I met my ex I was bubbly confident I love to work out. I always took care of myself, friendly compassionate, and pathetic outgoing and now I’m just a depressed empty shell.