Mzufall,
My situation mirrored yours in terms of taking good care of myself and still having a small child. I have only one child, a daughter. My current avatar is a picture of her at 14 weeks old. She was 3 weeks early and weighed a little more than 6 pounds at birth, 24 years ago.
My husband and I are on the short side (5'9 and 5'3). I fed my daughter as much as she would take, but I was never able to get as much milk into her as the pediatrician wanted. It was a source of constant stress to me until a visit we had with a pediatrician at Children's Hospital in Cincinnati. I wanted a second opinion on her growth. He said she's exactly where she should be. He pointed at my husband and me and said, "You're both on the small side and so is your daughter." That was such a relief to me.
Gngr-snap, the pediatric nurse, wrote, "Those charts are designed to compare a baby's growth to itself. As long as they are following their curve all is well. It is when they are <1% or >100% that a doctor will get worried. Typically a child doubles their birth weight by 6 months and tripled it by 12 months."
That was exactly the advice given to us by the pediatrician at Children's Hospital. As long as the child is continuing along their growth curve, all is well.
When the child starts precipitously falling below their curve, there may be neglect and/or a failure to thrive situation.
Amiah's body looks normal to me. I'm more concerned by the baby's withdrawn and emotionally flat expressions in the photos we've seen.