5 year old still having accidents in pants

[MiRaClEsExIsT]

Okay ladies, my son was a 25 weeker he is now 5 and a half. He has been potty trained since he was 3 but still has to wear pull ups at night. Every once in a while he will have an accident during the day and he says it's because he gets too busy playing or that at night he doesnt know when he has to go. I've talked to his ped and he says its normal and he will outgrow it. It's frusterating because during the day it happens at school or at daycare and I know he knows when he needs to go he just gets too busy playing. At night he is such a heavy sleeper that he doesnt kniow when he needs to go. I try waking him up but he wont fully wake up sometimes so he can go. I've tried cutting off drinks two hours before bedtime and he still is soaked in the morning. Help any ideas?!