Hi b, that sounds rough. With body dismorphia exercise will probably not cure you. Instead there will likely always be something else "wrong" with your body. You should look into therapy. If that's too expensive or scary, then at a minimum looking at your naked body in a mirror and telling yourself things you like about your body daily can help (even if they are lies at first).

That said exercise is still a good step for other reasons. Congrats for taking the first steps and being brave enough to post. Staying motivated while building healthy habits is deceptively difficult. It's important to build gradually, set reasonable short term goals, and reward yourself intermittently.

Obligatory if you want a more feminine physique and you haven't yet, check out r/sissyfitness because the FAQ is a good starting point. There's also something in the FAQs of this sub I think, but I haven't read it.