I need to go to the doctors for my back pain but I'm worried that she's gonna tell me to lose weight. I can't work out with back problems and I already hate how I look. I'm scared

Hello, I am having a hard time moving on from my past relationship. I regret losing my sweetest boy because of my disrespectful behaviour and attitude that I made. We broke up 2 weeks ago, and now I realize all my mistakes as lessons. However, I still regret it, and I’m struggling to change myself. I also can’t forgive myself. Can you give me some advice?