Hi My DS in 13, 5ft 6in with size 9 feet, which compared to his friends is about right, but he is 7st 6lbs and has not put on any weight for 6 months, it is like cuddling a skeleton, which he loves as he can see all his ribs. I only have 1 child so not sure whether this is a problem or not, he is healthy, a little pale, extremely energetic but just thin. Am I just worrying unecessarily?