What's wrong with my baby?

My daughter was born weighing 6 pounds 4 ounces, she dropped down to 5pounds 15 ounces at 3 days old and did not gain weight till 3 weeks old. Now she is almost 3 months an weighs 7 an a half pounds. Has anyone had a baby that is extremely small like mine? Btw I.was induced at 39 weeks because of low amniotic fluid, the only health problem we have found is acid reflux, she is in medicine that has helped immensely. She has also reached all her milestones, holding head up, smiling, ect but she is still 3 months old and the size of a newborn. She also eats well about every 2 and a half to 3 hours (breastfed) any tips on possible health issues would be great!