Night time nappy leaks

Hi all, 

My little boy is 6 months old and for the last week or so has leaked through his nappy at night. I had gone up a size so assumed it was that but he doesn’t leak at all during the day. 

He‘s active during the day and rolls all over the place but will sometimes sleep on his side at night. I have used pampers premium since birth and never had an issue until now. I tried pamper active fit last night but he still leaked through. It’s always the left hand side, seems to be above the nappy too. They definitely aren’t too full so I know it’s not that. I spend ages putting it on right and making sure it’s neat with no gaps, but it’s not making a difference. 

Any tips? Im fed up with the full change at 4-5am every morning!!! 

thank you

abbie