I ´m not sure of your context, but I ´ll see if I can help.
I ´m not used to knowing --- "used to" means "accustomed" --- so, also correct would be "I ´m not accustomed to knowing"
"knowing" here is used as a noun.
I ´m (I am) not used to milk for breakfast. I usually just have coffee.
I ´m (I am) not used to dancing before dinner. I usually just watch tv.
I ´m (I am) not used to waking up late. I usually get up at sunrise.
I ´m (I am) not used to walking to work. I usually take the bus.
I´m (I am) not used to knowing the answers. I still think I should ask for help!
used to + ____________ (noun, infinitive)
or another way to look at it --
used to + _______________ (thing or activity)
"Used to" can also mean something that you did in the past but you no longer do.
I used to live in Shanghai but now I live in Beijing.
I used to know the people in that building but they don´t live there now.
I used to be young but now I am old.
I used to run every day but now I work too much overtime. -------- Things that were normal in the past, but no longer happen.
used to + ____________ (verb)
Can you see the difference?
Hope this helps.