I too wanted to let you know that you are not alone! My son is almost 7 and still has accidents. We have seen a urologist and everything came back okay - he really just doesn't wake up at night as he is such a sound sleeper.
I would definitely recommend an appointment with your pediatrician just to have him evaluated and ensure that there isn't any problems - sometimes they have a bladder that doesn't empty all the way, but more frequently their little bladders just haven't grown enough yet.
Here is a tip that might help you. We were changing the sheets all too frequently and I found that everyone was getting frustrated... not because he was having accidents, but because of the work involved in cleaning up. My son started not telling us and then we would find smelly sheets.
So I sat down and explained that we understood that he might have accidents sometimes and it was okay. I also purchased 2 hospital grade bed pads that is soft on one side and vinyl on the other - if he has an accident all he has to do is throw the pad in the wash and he gets a new one out. This has really helped a lot.
I have also found that food/drinks can play a factor in more frequent accidents. We try to avoid alot of artificial sweeteners, soda, caffiene, etc. This doesn't eliminate it totally, but it definitely helps!
I have also considering buying the bedwetting alarm - it's a watch that has an alarm and it goes off if it senses the start of needing to go potty. I just haven't taken the leap to spend the money as I am worried it won't really help (it's over $100). Here is a link: http://www.bedwettingstore.com/Bedwe...ing_alarm.html