My son was born 8lbs 15 pounces and he is 2 months and is only weighing 10lbs 5 ounces.he is breastfeed and formular fed is this normal?

Generally, large for: Gestational age babies settle into a growth curve that's commensurate with their genetically-pre-disposed size. There aren't many 27 lb. One-year-old's! doubling birth weight by 4 mos. & tripling it by 12 months "holds" for -7 lb babies, but not always for 9 lb. Babies. Ask your pediatrician for weekly "weight checks" x 3 to establish his growth velocity, ~ 2/3 oz.-1 oz./day on his new curve.