At the end of january, i reached 87lbs and i upped my intake from 500-650 calories a day to 800-950 calories a day. on those 800 calories a day, ive gained in the last few weeks and weighed in at 93 lbs. why am i gaining weight and how do i lose?

The most common reason would be inaccurate estimates of what you are ingesting. Please meat with a clinical dietitian who can assist you in whatever program you are pursuing. That is, of course, after your physician has evaluated your health and agrees this is a reasonable idea. You don't give your height, so a random calculation of your BMI cannot be done to decide if a diet is appropriate.

You weight gain seemed to have followed the increase in daily calories (expected) and for your weight it appears that you are trending in the right direction. It has to do with your goals and possible conditions being treated, keep your physician and nutritionist involved in further decisions.

It would be unusual to gain weight on such a restrictive diet. It is possible that you are not measuring calories accurately enough. The previous doctor’s recommendation about seeing a nutritionist is a great idea. Drink plenty of liquids. Good luck.