For something we often did in the past, but don’t do it now, we say used to. But if we ask a question or put did or didn’t in the sentence then we say use to.
- I used to be a good player.
(Something often done in the past.) - Did you use to go to the same school as me?
(A question.) - I didn’t use to walk with my dog in the park.
(Did or didn’t.)
