Nappy keeps leaking!!

So my little one is now nearly 1.5yrs old and every morning give or take his nappy is so full with just wee and hes leaking! I’ve tried so many different brands and no difference, he’s on 5+ atm and he’s around 13.5kg so he’s in the right weight nappy. A friend suggested using pull ups at night and I’ve started this and finding it better but still ends up leaking some days!! This has only recently been happening for a few months now but I’m having to change his clothes so much now! Also he normally has a poo in the morning too after his first nappy change about an hour after. When I come to change this - it has most definitely leaked out all on his sides and on his bottoms! So I’m having to do 2/3 new pjs everyday! What can I do to help this, it’s honestly everyday with the poo nappies leaking even though I change it straight away and the wee night time nappies are now not as often but still often enough to drive me insane!!! Please help! Should I move him up a size? I do have 6 nappies and tried before too and was having the same problems?