"Δεν συνήθιζα να πίνω γάλα όταν ήμουν παιδί."
Μετάφραση:I did not use to drink milk when I was a child.
"I never used to drink milk when I was a child" is currently marked as incorrect, general strengthening on web. Perhaps the best translation - "I did not use to drink milk when I was a child" - sounds fine in American English, but it actually sounds completely wrong in British English. I know sticking a 'never' in there implies that there should be a ποτέ in the Greek, but 'didn't use(d) to' sounds very wrong to me.