Hi Olga I personally don't use the term "didn't use to" often. When talking in the past, if I used to do something for example, going to church as a child, I could say the following: "I used to go to church when I was a child" - this would be taken as something I did often. "I used to go to church sometimes when I was a child" - adding "sometimes" would let the listener know it was something that I did, but not often. "I never went to church as a child" - to state something that you did not ever do in the past. If I were to say "didn't use to" do something, it would be in a situation where I do that action in the present. For example: I didn't use to smoke, but now I do. I didn't use to jog, but my doctor said that I should start exercising to stay healthy. Otherwise, if it is an action I never did in the past, I would use "never" I never went swimming as a child I never stole anything in my life. I never took a French course in school. Hope this helps.

Hi Olga It sounds OK to me. "I didn't use to like milk" and "I used not to like milk" are interchangeable in my opinion.

"used to" is the past form for usually. When you had in the past one costume something that you did very often you can use "used to". If you are talking about an habit in the present you'd say "usually".