"Used to" has two meanings, and we use different forms of the verb for each meaning. When used with the present simple verb, it means something that was typical or common in the past (e.g., "I used to live in Shanghai," "He used to work at Microsoft," "She used to have a cat named Kiwi," etc.). When used with a gerund (-ing ending) verb, it means to be accustomed to (e.g., "When he moved to England he had to get used to driving on the left side of the road," "She is not used to waking up so early," etc.). The form of the verb tells the listener/reader which meaning is being communicated, so it is important to get this right.

I used to do something = 我以前做 I am used to doing something = 我慣了 I am used to do....is incorrect!

I used to + verb = 我以前。。。 I used to do something = means in the past, I would do something a certain way ... it's often used to describe something you did in the past but no longer do. example: I used to like playing sports, but now I don't. I am used to + noun／verb - 我習慣。。

used to do something means he used to do it in the past , but now s/he doesn't. i used to smoke.( now i don't) be used to doing something means s/he is familiar with this thing, accustomed to doing this thing. i'm used to living alone. he is used to the darkness. means he doesn't fear darkness.