What size is he in?
My kids went up a size well before the end of the weight range (in sposies and MCNs) because they had long bodies mostly.

Could be a faulty batch too.

Woolies/Safeway homebrand and select nappies were ok with my boys, as were comfy bots.

I can also second that pampers are great. They look thin but are pretty absorbent though I did had ds2 fill one to bursting but he did that with all the brands for a while there.