Low BMR - need help

I am 36, 5'6", 160lbs. I had my RMR tested at the gym yesterday and the result was approximately 1000 cal. I am looking for suggestions on a number of calories to eat and to burn through exercise. I have been working out approximately six times a week and burning on average 500 extra/exercise cals a day. Based on many online calculators, I had assumed my RMR was almost 1500. I have been eating anywhere between 1700 and 2500 cal, and not losing, nor gaining, any weight. I also intend to see a doctor about blood work, I would appreciate any suggestions as to what type of tests I should look for. And RMR of 1000 cal at my height and weight seems very low.
Thanks!