I think I maybe suffering from anorexia nervosa?

First off, I am person who is way overweight but my family tells me that I'm just a little overweight but I think I'm huge looking everytime I look in the mirror. I have a major big fear of becoming morbidly obese or just gaining weight in general so I am eating just one meal a day and walking for an hour 2-3 times a day. And I have lost some weight doing this as well. So I would like to know is is that callled anorexia nervosa?