C.B.
Bedwetting at 4 is not unusual.
But in any case, explain that if he continues there's no other choice than to wear a nappy or pull up. Tell him it wakes you up out of sleep which isn't good. And that he isn't learning to get up himself. If he doesn't want to wear a nappy or pull up, then he has to stop.
Explain that he only has so many sheets available and you can' t keep up with the wash. same with jammies
You have to eliminate the liquids before bedtime. Even if it's from dinner time onwards. Milk is fine. That will help him sleep.