Who can have eating disorders? Do I?

I’m not overweight, nor am I underweight. I’m 18, 5’1’’ and weigh 118. I have 13% body fat. In August, when I started college I weighed 133. I’m on the field hockey team and started to work out before and/or after practice because I never felt like I was getting enough at practice. At the beginning of November and the end of field hockey, I started to become obsessive with the calories and food I ate. I started to work out more than ever, twice a day, sometimes three times. I already can’t eat gluten nor dairy due to medical reasons but I cut out everything else and only eat fruits and veggies. Near the end of November, I was only drinking liquid and nibbling on a few pieces of veggies a day. I started to count calories and at the end of November I lost 15 pounds and weighed 118.

I’m home on break and still count calories but I have to eat a little more than I had. I eat around if not less 800 calories a day but only at night (I end up throwing some of it up). I go running and base my workout on the amount of calories I lose in the morning and before I go to bed. My sister is worried about me and keeps telling my parents there is something wrong and that I have an eating disorder. should I go to my doctor? =/