E.,
This is a very sensitive subject for me. I was a bedwetter until I was 18 years old! My mother was well into her 20's as was my grandmother. My son is 9 and is still wet probably 99% of the time. Here is the response I have given so many other moms. I am not saying this will be your son at all, just giving you our experiences.
"I don't really have any help for you other than to let you know that you are not alone. My son has been a bedwetter since day one, and can tell you that with him the only thing anyone wants to do is give him one of those alarms you wear on your underwear. I had one as a child and my problem got worse so I do not reccomend them at all.
Anyway, bedwetting can be caused by numerous things. Not enough of the hormone that "shuts down" urine production at night, too small of a bladder, an over-active bladder, and on and on. Do understand though that typical bedwetting is not considered a problem until children are about 8 years old (and even then, NOT a big deal until AFTER puberty)!
The urologist we saw said to cut way back on caffine, chocolate, carbonation, and citrus...cut out liquids after 4pm and only small amounts with dinner...make sure he uses the bathroom EVERY 2 hours and sits/stands for at least 2 minutes every time (to make sure the bladder is completly empty), and most importantly that the problem would not change if the child did not think it was a problem. My son is also 9 and wets the bed nearly every night. I have a waterproof protector on his bed and I wash sheets daily (as goodnights are WAY TOO expensive to use every night). My son does not feel his bedwetting is a problem so he is not ready to make an effort to change. So as much as I push, he will not use the restroom every 2 hours, he will not stay in there for 2 minutes, he sneaks drinks well into the evening...so I have stopped fighting. I figure as long as nothing is medically wrong (and we have had many tests), and he is OK with it...eventually he will decide that this is not what big boys do. Until then, I have choosen not to fight this battle.
Sorry I'm not much help. Just wanted to let you know what our experiences have been. Hope you get some answers."
Anyway, hope that helps. Just don't expect too much from him too young. My daughter is 7 and has been dry 99% of the time since she was probably 3 or 4. I guess what I am saying is that it is different for everyone.