He sounds fine... babies will lose much of their water weight quickly after birth - which is necessary since they are no longer living in an aquatic environment. Tell your Pediatrician that unless he notices other major symptoms - such as dry tenting skin, pallid skin tone, lack of muscle tone, sunken eyes, dull stare or lack of voiding - that he call it a day and let you and son get on your business of bonding, sleeping and nursing.
They are using formula fed charts anyways - which are very different. Formula makes babies fatten up more because the proteins, fats and nutrients are synthetic, souped up to the highest legal rate and foreign proteins - which makes it harder to absorb, yet all the sugar and fats in the formula make them gain weight quicker. Your baby is having the normal nutrition, which isn't covered in medical schools... and they have no clue what they are doing. Maybe you should ask if they have a more breastfeeding knowledgeable and friendly pediatrician, or search for one.
Try to relax and enjoy your newborn - sounds like nothing is wrong except he's not getting as fat as formula fed babies your Dr has dealt with... which is normal and absolutely fine! To ease your mind, get in contact with an IBCLC, not a run of the mill LC or CLC and have her check your latch and measure how much baby is consuming. I'm sure that will make you more at ease.