Reasons for significant weight loss?

i have lost over 40lbs in a short few months. But that hasnt been my goal my goal has been to maintain that 145lb weight. but as each month passes the more i increase my food intake i seem to loose more and more now i am down to 101. See the Difference 145 to 101. I have had my thyroid check , spoke with a nutrionist , all std and other factors have been check and everything has come back fine. So please help I need to think out side the box and these doctors just keep asking well do you eat. Duh dummy of course I eat lets get more technical please cause I dont know what else to do and apporintly neither do they.