DS is 3.58kg ...been using pampers size 1 for 2-5kg babies and I'm constantly getting wee up his back and soaking through babygrow! Tried the size 0 just in case it was too big and same issue. Tried pulling frills out, tried tightening it, tried lifting the back up more...is the nappy too small ?! Can't be surely...
And how does it leak up his back! Very sleep deprived and tired as he is only 2 weeks old bless him 
Thank you in advance!