This question already has an answer here:
Here is a question that has been nagging me for a few years: Which is the right usage: "Didn't used to" or "didn't use to?"
Examples: We lived on the coast for years but we didn't use to go to the beach! We lived on the coast for years but we didn't USED TO go to the beach!
He didn't use to read stories as a child, but he grew up to be a writer. He didn't USED TO read stories as a child, but he grew up to be a writer.
Did you use to play video games in your youth? Did you USED TO play video games in your youth?
I have seen this question asked on many other websites, and there has been a great deal of debate, but it had generally been inconclusive.
I personally consider 'didn't USED TO' a wrong usage, but would like an expert opinion.