Used to + infinitive
We use used to + infinitive to describe habitual past actions.
- I used to ride my bicycle to school.
- I didn't use to catch the bus.
We also use used to + infinitive to describe past states.
- He used to believe in Santa Claus when he was very young.
- She didn't use to have straight hair. Her hair used to be curly.
We use use to + infinitive with the auxiliary did/didn't in a question or negative statement.
- A: Did you use to play basketball?
- B: Yes, I did. / No, I didn't.
- I didn't use to like spinach. Did you?