can not gain weight

Im 72 pounds and I have tried to gain weight I can eat and eat and not gaining anything my dr says eat healthy which most of the time I do or just eat..eat.. she wants me to be 80 pounds I do have a digestive systems which is consptaion all the time . I have always been skinny and a little bony in some places.
what can I do to help me gain the weight that I need  please help ?

[James G Beckerman, M.D.]

Eating and drinking high calorie foods is the way to go - and there are many healthy options that will also help you pack on pounds.  But the obvious concern is why you only weight 72 pounds...?  It is very important to try to understand this with your doctor!