When talking about things that we did in the past but don't do now we can use the expression used to. The negative form, to talk about things which we didn't do in the past but do now, is didn't use to.
Used to and didn't use to are only used to talk about past habits. There is no present form. To talk about present habits we can use the present simple. When using these structures there are often two parts to the sentence, something about the past and something about the present.
