Used to

The auxiliary ‘used to’ expresses a discontinued habit. It can also be used to talk about something that used to exist in the past.

There used to be a house on that lot. (That house no longer exists there.)
I used to live there when I was a child. (I no longer live there.)

In questions and negatives, we are more likely to use ‘did you use to’ and ‘did not use to’.

Did you use to live there when you were a child?
I did not use to eat meat when I was a teenager.

Need

The auxiliary need shows necessity or obligation. It can be conjugated with or without ‘do’. When it is conjugated without do, it has no –s or –ed forms and it is used with an infinitive without ‘to’.

He need not go. (NOT He needs not to go.)

But you can write: He does not need to go.

Need I talk to him? (NOT Need I to talk to him?) (NOT Need to I talk to him?)

But you can write: Do I need to talk to him?

Note that when conjugated with do, need has the usual forms needs and needed and is used with a to-infinitive. It is commonly used in questions and negatives. Sometimes it is used in the affirmative as well.

Do I need to go now?
You don’t need to wait any longer.
One needs to be careful.