Should i loose weight?

well i am 13. 165 cm (5.5 feet) and 57kg (125.4lbs) i have a stomach and im a little bit chubby so do i need t o loose weight? or am i overweight? my doctor says so but when i check on the online calculators they all say im not overweight(iv tried over 50 different websites)oh and i think my body fat percentage is higher than muscle so if it is could you also tell me hwo to loose body fat very fast? thanks