What is wrong with me? I am showing behavioral signs of anorexia but I'm not anorexic. ?

I am not saying I am anorexic, but I've been having some issues with myself for as long as I can remember. I haven't eaten in 3 days and have lost 10 lbs. (I am now 5 foot 6 and 140) I am a very muscular and big boned girl and everyone always says how great of shape I'm in but I see myself as huge. I go through phases like this that last about 4 months all the time. I don't starve myself and I do eat when I need to. I have this willpower not to eat and I get extremely upset with myself when I do eat. My menstrual cycles have also stopped. What is this?