Struggling with Body Image After Coming Off Sertraline

Recently come off sertraline after 4 years and have been having a lot of negative thoughts over body image. In those 4 years of being on sertraline, I've put on 3 stone in weight and hate the way I look. I do walk a lot but find I struggle with eating the correct calories. I over eat a lot, I just really like food. I got upset about it the other day saying how much I hate the way I look and my partner suggested I may have body dysmorphia. I'd never imagined myself to have dysmorphia but it kind of makes sense. I look in the mirror and I see an imposter in my own body. I picture myself as that one from before my antidepressants, one which was 3 stone lighter and could fit into clothes easier. I was fitter back then, I didn't get out of breath doing certain things and I didn't have plantar fascitis either.