Is this a new occurrence of bedwetting or has he always frequently wet the bed? I ask because it may not be from stress but genetics. All the men in my house,(husband and two sons) were bed wetters until around 8 or 9 years old. My youngest will be 6 next month and also wets the bed frequently. First of all, do not shame him or scold him for it. Usually it is nothing that he can help. Often boys, for some reason, have immature urinary systems. They simply do not get the signal from the bladder to the brain to wake up to urinate.
I have discussed this with my pediatrician several times. We both agree that he will grow out of it in a few years. In the mean time, you are doing the right thing, limiting drinking for several hours before bed and making sure he goes right before bed are definately in the right direction.
Two other ideas is to cut out caffiene. It can also affect the urinary system and cause issues at night. They also make a bedwetting alarm that will wake the child up when he starts going during the night. I do not know about the price of it though. I have not invested in this but I do have mattress covers- waterproof of course, and I do a lot of laundry. My best suggestion is to buy extra sheets and wait it out.
If this has just started consult your pediatrician. There may be other reasons for it that you have not thought of. Good luck and know that you are not alone!
Jessi