My 16 mo son has had pale yellow stool since his birthday, i called his pediatrician who said it should go away. it hasn't and is getting lighter?

Yellow stools: As long as your baby is completely well, then i would give more time, to change to normal. Besure he is not getting something in his diet that has yellow coloring in it.

Gaining Wt well?: I would tend to agree with your pediatrician. If he is eating well, and gaining weight well, i would not be too concerned only about the color of the stools.