leaking diaper

I am new to this,i was wondering why it was leaking in this spot isn't it supposed to be waterproof. do it look like I need to change his diaper more often? or has it come out the leg hole? this was after 3 hours I think.

it's a wrap with an insert and a fleece liner. I can't fit a booster in as well there's no space. it's already leaving quite bad red marks and I'm worried it's too small.