Do I have an eating disorder, maximum of 500calories per day

I am wondering if I have eating disorder I only eat one meal a day which is normally dinner only because I have to and I count every little calorie, I have set up a food diary to be a maximum of 500calories per day and each day I try to burn more calories than I consume. I use diet pills and on the odd occasion laxatives. I check the nutrition on everything I eat and if I feel as though it is too much I will not have it. I get very anxious when others cook meals because of not knowing how many calories are in there exactly. Even when others express concerns about my weight or comment on it, I deny anything and say that I am still fat or grab at what I think is fat but they say is skin. I am 5ft 6 and currently weigh 105lbs I am 22 years old.