Hi ladies, I have a almost one year old and we have always had the weight battle!! Just listen to your doctors, and your gut instincts and feed them as often as possible
DS was a medium sized baby at birth (7lbs 2 oz), and dropped a fair bit the first few days. After a week he began putting on a little bit of weight, and then gained up to his birth weight and above by maybe 3/4 weeks. After that, we were brought in at least every 2-4 weeks for a wieghing and it stressed me to the core! I dreaded the weigh in. Other than weight, he was progressing fine, meeting milestones before expected, he was alert and happy!
Finally at 9 months we had a weigh in and again he did not gain what they wanted, so they started FTT (Failure to Thrive) tests. I ws gutted and a nervous wreck the whole weekend while waiting on the results. When the Dr finally called, he said that they would leave me alone as his blood count, and organ tests that were done showed all was healthy and normal. He was not lacking in calories, or nutrients etc (although his iron was a bit borderline). So after all that stressing, the doctor said he is fine and healthy, and just a little guy!
He has been breastfed and on solids. I asked if I should have used formula and the Dr said no as BF is better if the mom is able and wiling.
So, in conclusion, some babies are small! I'm not saying to disregard what your doctor says. You should listen to them, but from a momma who has been stressed since he was born about the whole weight debacle, it might be alright
Good luck!