Ds is three and seven months, 98cm and 13 kilos, as he has been for ages. The NHS BMI calculator puts this at 1st centile and 'underweight'. I don't really want to discuss with our HVs who we haven't seen since he was one - should I worry and in any case what can I do? He has plenty of energy, though is very bad tempered, eats a reasonable amount & I was skinny too. What do you think?