hi rhonda--
our son just turned 5 in march and he has gone through a similar cycle.
he began staying dry all night right around his 4th birthday last spring but around christmas he started having accidents again. we had totally stopped nighttime pullups & he was in regular underwear all night. when he started having accidents again we went back to pullups for about 4 months. he is now dry most nights (5-6 nights out of 7).
what we have seen is that when he is really tired he is more likely to wet the bed. also, we only let him have one drink after supper, usually water, about an hour before bed, and then he has to pee before he gets in bed, whether he has the urge to or not. this has worked well for us. he sometimes gets up in the middle of the night to pee but this is only when he isn't totally worn out. if he is exhausted he doesn't wake up at all until morning and that's when he is wet. if he is generally well-rested he stays dry all night.
i'm not convinced that limiting his fluid intake during the day is going to help him at night. your best bet, in my opinion, is to look at his evening fluid consumption. this time of year, in particular, you really want to be careful not to let him get dehydrated--so making him cut back during the day probably won't help, and may be a problem. around dinner time & afterwards is when you want to limit his fluids. we have found that getting CJ to go pee right before bed has had a great impact on his ability to stay dry all night. and it helps psychologically too--when we forget to make him pee, he reminds us that it needs to happen. he feels much more in charge & in control.
good luck, hope that helps a little!