Why my house broken dog keeps goin to the bathroom in the house?

I have an almost three year old dog, I believe she is a terrier, blue healer mix. She is outside all day and evening, comes in at night. We have done this since she was a puppy. She had very few accidents in the begining now within the last month she has been going poop and pee in the house on a nightly basis.We have had her since she was a puppy like 2 months old. Not understanding why she is doing this or how to stop it. No changes in her house.