My 11 month old son sweats excessively while he sleeps or cries. He sleeps in only a diaper and uses a sheet or no blanket, but still leaves pools of sweat on the mattress. Is this something to be concerned about? He is of average height/weight for his age, development is normal, but he has had a few medical issues since birth: pulmonary hypertension at birth, reflux until 6 months, intussuception at 5 months, some neurological concerns but EEG was normal, and reoccurring ear infections (tubes at 11 months).