Puppy pees on the ground for attention?

ok so i have a 3 and a half month old golden retriever puppy and i've taught him a lot of tricks and his housebreaking has been going great. there's just been one thing that i can't figure out. i take him out every hour or every hour and a half and so and he obeys me completely peeing outside. the problem is, every time i leave him alone for a while in a room where he can't chew stuff up for like short periods of time, (like 5 mins to get his food) he whimpers and pees even when he peed like 20 mins ago. i usually come back to him when i see he pees to clean the mess up, so is it possible that he ociates peeing on the floor when im not around with me coming back? if so, how do i correct or react to this? if not, what else could be causing this? he doesnt do this always, just when he wants me to be around him. oh, and about him being alone in the room for like 5 mins, thats only for that amount of time he's alone, he's allowed anywhere else in the house after that under my supervision, it's just so he cant destroy anything while i'm getting his food. i spend most of my time with him and i'm gone very seldom. i also ignore his whimpering but dont know what to do. help?