I would go to a doctor to get tested for worms/ parasites first. If that is not the issue, then it's likely the way more common problem of Pruritus Ani. This essentially means you just have a chronic itchy bum being caused by any number of things. There are a few products out there that treat Pruritus Ani--by far the best one out there is called Pranicure. You can only buy it online. I used to wake up in the middle of the night to scratch but after using pranicure for about a week and a half I can sleep through the night again. I'd definitely recommend you try ordering some.