During my school days, my English teacher taught us that there is something called double past. For example - you don't say -
- I didn't went to school yesterday. -> He said with didn't you don't use another past verb form.
So, he corrected us
- I didn't go to school yesterday.
Now, I am a bit confused here.
Incorrect Sentence - 1. She would hold my bicycle from the back to ensure that I don't fell down.
She would hold my bicycle from the back to ensure that I didn't fell down.
I am confused here - didn't + fell -> isn't a double past?
What am I missing here? I have seen that I do this mistake a lot. Please help.