Your story is not uncommon. Many women who have been raped, and not gotten proper counseling, put on weight because either consciously or subconsciously, they know that the extra weight tends to make them unattractive to most men. That way, the thinking goes, men won't bother them.
Please do all you can to get proper counseling. If you haven't yet, go to http://www.rainn.org
for help in locating a good counselor. If you are not in the US, the folks at RAINN can point you in the right direction when it comes to counseling in your own country.