Hi.
Long time no see. How have you been doing?
Maybe either way is correct? See the usage of its negative form below:
used to
Adjective
accustomed to: I am used to being a medical guinea pig
Verb
used as an auxiliary to express habitual or accustomed actions or states taking place in the past but not continuing to be the case in the present: he used to vanish into his studio for days
USAGE/b>: The most common negative form of used to is didn't used to (or didn't use to), but in formal contexts used not to is preferred.
URL: http://www.thefreedictionary.com/used+to
