At your age the weight is definately worrisome.Does your diet consist of entirely of fried stuffs/colas/candies? If yes you need to cut down on this and start a fitness programmeASAP.If no you could be on a low thyroid
status-check your blood levels of T3 T4 TSH
. and proceed further .Else you could do a metabolic level check visa vis blood sugar levels -to rule out diabetes
.See if this helps.