Can anyone help me??

my son has decided that at night he only wants to sleep on his side. He is a heavy wetter overnight so we usually have to do a change but lately he is leaking through nappy, clothes, sheets within 1.5 hours of a change its driving me crazy as i have to change him over and over again and then resettle him. He is in Huggies crawler hes about 6.5kg and we've tried both size up and size down but no difference.

I'm thinking of getting a cover but that will take a bit of time so if anyone has any immediate ideas or alternative one that would be great

Hope this made sense slight sleep deprived