Nappy’s

Looking for some help / advice. My 2 year old son is currently in pampers nappys, I have tried him in size 4, 5 and 6s and when he has a poo it is coming out the sides of the legs with all three sizes. He is also getting a regular sore bum which he is finding very distressing. Has anyone got any recommendations of other nappies to try or what I can do differently? His poo isn’t loose but there is a lot of it and it’s smells pretty bad, health visitor recommended to reduce his dairy down which is have but doesn’t seem to have made much difference. Willing to try other brands of nappies but don’t want to end up trying loads and getting the same results.