New to this very scared n overwhelmed

All my life I was in shape. Since 13 I have suffered with bulimia but had it under intros after I had my daughter however a year ago while training at the gym 5 dys a week I suddenly started putting on the weight n neither my dr or my trainer old understand why. Turns out my thyroid had shut don allowing my metabolism to join. In one year I put on over 100 pounds. Now I'm 265lbs my bulimia is out of ontol n I hate looking at myself I'm starting at the gym again tommorow slowly but it's so depressing.