Maybe he's incontinent and is trying to use a pad to stay dry.

Perhaps he is fearful of sharting.

If he is old enough to know what they are for, maybe he lost a bet with one of his friends. This was the payoff.

Maybe he wasn't feeling well that day and was afraid he might have a bathroom accident. He could have used the pad as a backup just in case.

I did this when I was little, for me it was due to the fact that I liked how diapers felt back then and pads were the closest thing to it. see how he reacts when u give him a diaper and then you'll know.

I'm gonna throw this out there, I borrowed my sisters pads because I was literally too sick to get out of bed and my parents didn't have a bedpan, so they saved me from a couple accidents. Being sick and immobile makes you resort to embarrassing things. Although maybe he's afraid of poop stains? Heehee

Depending on what, if any, kinds of stains were on the pad will give you an idea of why he's doing it. If it's urine or fecal stains, it's a hygiene thing. No stains could be sweat, support, or curiosity. If it's blood, he could have a kidney injury, hemorrhoids, or he could be intersex and have had a period, which isn't unheard of. Obviously, if there's blood stains, you need to talk to him and take him to a doctor.

I have guy friends who carry pads with them, mainly because us female friends are never prepared...... it is a really good strategy too, they have gotten girl friends from it.

swamp ass?

Maybe he likes the extra padding?