Past continous
1. I was working with my computer when she walked in.
2. While he was cooking for her, she already waited for  a long time.
Yah pokoknya kalo past continous itu untuk long action

Used to:
1. I used to ride my bike to work.
2. Now you're just somebody that I used to know. <<< lagu
3. She used to be my friend.
Pokoknya used to itu untuk membicarakan masa lalu.
 What were you doing at 8:00 o'clock last night? ,, I They were studying math yesterday was writing a lesson all day, yesterday.  We were going out all afternoon last Sunday ,,When you called me, I was studying English.