Urine infection or potty training regression?

[tortilla]

DS (3.5) has been potty trained for 7 months. He wasn't easy to train but was dry day and night since then, apart from one regression of a few days when we were on holiday and he was jetlagged and a bit confused.

We have had getting on for 2 weeks now of at least one wee accident per day. At first I thought it was a regression because his key worker and best friend left nursery and then we went on holiday for a week and he has just started a new preschool this week. But I am beginning to wonder, as he has been really brilliant since the last regression which was 4 months ago, and today he has had 3 accidents, one of which was basically a sprinkle on the carpet while naked (he NEVER has accidents when naked, only when in pants as if the pants can catch it) as if he just couldn't hold it in and he has weed 4 times since he came home from preschool at lunchtime which is very unusual for him (he is a cactus and barely drinks so usually only has about 4 wees a day never in just 4 hours)

Anyway after the last wee I asked him what it felt like when he weed "spikey, stingy or sore" and he immediately said stingy. Now this could just be a 3 year old choosing his favourite word out of the 3 I gave, but it does make me wonder if it is a urine infection as that would be a reasonable word to choose.

No other symptoms though - eating well, no fever, not particularly under the weather etc.

Any thoughts?

He may have a willy infection.
My ds (4.2) suddenly wet the bed every night having not wet it at all for a year. took him to the Dr. (who said regression like that would always be taken seriously as something wrong) and gave his cansten for his willy. He hasn't wet since. He said his willy was sore, and kept poking it, but had no other signs.

Thanks! He spent most of the holiday naked (oh to be 3 again!) and was playing with his willy a lot (i.e. constantly) - assumed it was because he had free and easy access but maybe it was sore. I just asked him again if it hurt when he weed and he said yes and when I asked what it felt like (no prompting this time) he said it felt like stinging nettles :( but :) at the good description! So I think we'll head off to doctors tomorrow.