My 15 year old son has over the last month or so has passed a lot of urine. He can go hours with out going some days and other days if he drinks a standard size can of coke for example within 30 mins he will need a wee after going then for the next hour or two he could go 3-4 maybe 5 times with an almost full bladder. Not ideal for car journeys or his school trips. Haven't taken him to the Doc yet. Not an infection no pain or anything. Any ideas? He's an active average built teen