I've had the same problem - weight and thyroid problems. This may come as a surprise but many people, especially women who are empaths or psychic have thyroid problems. Apparently, the glands play a role in the transmission of psychic information.
At this point, my weight will not go down, regardless of how little i eat or how much I exercise. The body is going to do what it's going to do. Within a week, I gained eight pounds (most of it's water) without adding anything into my already strict diet; I've even been exercising more. I do know that I am very tense and haven't slept well which is probably a factor.
As to the bully, I've dealt with it all my life and it hurts. But when i finally accepted that this is my body and it really doesn't want to change; then the insults don't bother me as much. So, I'm fat - so what? I like the comment Lady Gaga made after she was criticized for her weight; she said "I'd rather be fat than shallow."
Trying to fight a bully is tricky; clearly they feel awful about themselves so they project those feelings on to another. Shame tends to be one of those feelings that is easily projected and if you're feeling uncomfortable about your appearance, you become a magnet for those comments. You are blessed with a great body that will do it's best for you, it may never be like other bodies but remember that standards of beauty change. When you can accept yourself as you are; the battle is over.
Some people visualize some type of barrier around them, like a wall of mirrors facing outward, so that his energy would bounce back at him. Other ideas are to connect to Source and just ask that this issue be removed. And, if you can; you stand your ground and you give it right back in his face. You have to take all that emotion he's throwing at you and throw it back at him.
But it's about what you feel comfortable doing. Remember that you are the one with the power - as an empath, you can sense his feelings, where he's vulnerable. That alone, is powerful; you have the advantage over him. It will be your decision as to how to handle it but remember, that you have more power than he does. That information, alone can help you change how you feel about the situation. You're feeling powerless because you're picking up his sense of powerlessness. When you realize how much power you have, it changes the energy of the situation.