Follow your gut and get it checked out. I have a special needs daughter so I know all about fighting for the best interest of your child!
I would call your doctor's office back and ask if they take all kids ins. If they don't then you are going to have to find another doctor anyway.
If they DO take all kids, then insist on speaking with YOUR doctor. You have that right! Insist on getting whatever testing just to rule out any health issues. B12, thryoid. Personally, I would ask them to run a full chem panel. That way you are only drawing the blood once.
JMO, but if a doctor is not willing to listen to a parent's concerns, then that doctor is not worth going to. As our doctor says, "moms always know best, since they KNOW their kids".
Good luck and keep us posted!