Moms, I need some advice please. My son will be 1 month on the 1st and he was 7.78 pounds and 20 1/2 inches long when he was born and dropped down to 7.4 in the hospital then when I took him to his 1 week appt he jumped back up to 7.54. Then Tuesday I took him to his doctor and he weighs 8 pounds 2 oz and is 21 in long.. His doctor said he is a little under weighed.. I now feed him 3 oz every 3 to 4 hours and she said that was great so I'm wondering why he's under weight?