I'm Obsessed With Couting Calories!?

I have anorexia but i also purge and on some occasions binge so you could say i'm binge/purge anorexic,but for the last few weeks i've been purge free and i'm so happy about that. The problem is the only way i've been able to do this is record exactly how many calories i am eating each day and i can't go above 1500. I'm underweight with a BMI of 15.5 and when i went to the ED clinic yesterday i had lost 2lbs in one week bringing my BMI down to 15.0. I'm 16 btw. I'm scared that now i have got rid of the bulimia i'm now going to be a full blown anorexic. I don't want that! but the only way i feel i can cope with not binging or purging anymore is by having a strict calorie controlled diet. If i don't know the exact amount of calories in something i feel anxious and that leads to me throwing it back up