Is his wee smelly at all? Get them to check his urine for a UTI. It's a simple non-intrusive test, if they say it doesn't need to be done...demand it. At least that's something you can rule out if it comes back all clear. It could be something as simple as teething, but it's better to be safe then sorry I am only passing this advice on as my son had a couple UTI's when he was younger (starting at 10 weeks old). The doctors took ages to test him for it as he only had fevers and no other symptoms. They told me he should have been in pain and crying, off his food, very smelly wee.....he had none of these.