I have two SW CAH boys, my youngest was very skinny and small.  He is still small but not so skinny.  He is 6 years old now and is a very normal weight,  I think 50%.  Anyway when he was between 9mos and 2 years or so he was not on the weight chart,  it made me a little crazy too.   My Dr.  never seemed to worry as his levels were good,  I even met with a nutritionist.  He just slowly started eating and now he loves everything, now I have to tell him he can’t have another snack,  I used to let him eat whenever he wanted.

Good luck to you.  It is easier to be skinny than have weight being an issue on the other side,  if levels are good try not to worry.