I mean that you need to know how much you burn in a day and how much you consume. If you are not losing weight, you are not eating less than you burn, so one of those two numbers is not valid/correct. Your doctor can determine if you have a rare medical condition that causes a very low calorie burn. That's unlikely since you have been able to lose in the past and also because these conditions affect energy levels and ability to function normally. It is possible to have a lower than average metabolism and burn less than most people your age, height and weight but that is usually a difference of well under 10%. The other number is intake and if you weigh portions and track every single thing that should not be far off.