Here you are using ‘not used to’ to inform someone that you are unfamiliar or uncomfortable with a topic at hand.
Here are some examples:
“I’m not used to talking English.”
“I’m not used to studying so much.”
“I’m not used to being around new people.”
“I’m not used to talking in front of groups of people.”
“I’m not used to having so much stress.”
“I’m not used to traveling so much.”
“I’m not used to working so early.”
“I’m not used to having so much responsibility.”
“I’m not used to drinking so much.“