You can only say "I used to do X" when you no longer do X.
1. I used to eat pickled onions in bed.
(In the past, I regularly ate pickled onions in bed; but now I no longer do so.)
2. I used to open beer bottles with my teeth.
(In the past, I regularly opened beer bottles with my teeth; but now I no longer do so.)
This structure shouldn't be confused with "to be used to doing something", which means "to be accustomed to do something", e.g.
3. I'm used to getting up at 5 o'clock every morning.
(I am accustomed to get up at 5.)
- For Teachers