Alternatives to the common construction "didn't used to"

I am hearing the use of this odd-sounding construction more and more frequently as of late. For example:

I didn't used to smoke.

I didn't used to work for McDonald's.

I was trying to think of alternatives to this phrase but all I could think of was previously:

I didn't previously smoke.

I didn't previously work for McDonald's.

That said, to me, the use of "previously" instead implies an event took place that changed the fact in the statement. In other words, to me, "previously" is more similar to "prior to (something)," whereas "didn't used to" refers to the general past.

Are there any better alternatives to that of which I have already thought?

I see nothing wrong or odd with the following sentence and its meaning.

I didn't use to smoke

This statement means I was a non-smoker in the past. It implies that today I smoke on a regular basis. When we want to contrast a repeated action in the past that is no longer true in the present, used to, is a perfectly valid construction. Compare the same sentence in the affirmative

I used to smoke

This means I was a smoker in the past, but now I do not smoke. To make the past simple negative form in English use did + infinitive verb

Examples:

I didn't smoked I didn't smoke

He didn't played football. He didn't play football

We didn't went to the match We didn't go to the match

Likewise with used to, the negative form in the past simple is didn't + use to

The difference between didn't use to and didn't used to is not noticeable in speech but this error (and it is an error, I don't care how many instances Google says otherwise) is replicated in writing.

The story is a little different with the second example (corrected)

I didn't use to work for McDonald's.

Here the speaker is saying he didn't work for an extended period for or in a McDonald's restaurant. However, this implies he is working for that company today.

A: Bla, bla, bla... What are you doing now?
B: I work in McDonald's
A: Really? But didn't you leave college with a Bachelor's degree in X?
B: Yeah... Listen I know it sounds weird, I didn't use to work in McDonald's but now I do. It's a long story.

Macmillian Dictionary says:

Used to only exists as a past tense. Questions and negatives are usually formed with 'did' + use to (with no 'd'): Did you use to work here? ♦ We didn't use to earn much. The spelling 'did used to' is sometimes used, but many people think that this is wrong. In formal English, negatives are often formed with used not to:
They used not to allow shops to be open on Sundays. The short forms usen't to and usedn't to are sometimes used, but they sound rather formal and old-fashioned. used for saying what was true or what happened regularly in the past, especially when you want to emphasize that this is not true or does not happen now

• I used to enjoy gardening, but I don't have time for it now.
• They always used to ring me and say what they were doing.
• Where did you use to live before you moved here?
• I didn't use to like him, but now we're good friends.
• Customers didn't use to want to shop from home.

If you want to substitute "didn't use to" say never.

I never smoked but now I do

I never worked for McDonald's but now I do

Alternatively, as suggested by @Peter Shor in the comments below

I never used to smoke

I never used to work for McDonald's

Didn't used to is the correct negative form of used to, but only in spoken English.
That's why you keep hearing it; it's normal, correct, grammatical, and very very common.

The problem arises when you try to write it. This is of course not part of English grammar, but rather of English orthography, a Rube Goldberg construction with as much grace and utility as a scrap heap. Which is what it is -- spellings have been piled higher and deeper over the centuries.

Herewith what I said about this particular problem in the context of another question:

My favorite example of where writing gets in the way of language is how to write the negative of used to /'justu/ as in I used to like it /ay'yustu'laykət/. The problem is whether the negative should be written

• I didn't used to like it.
  or
• I didn't use to like it.

To me, at least, both spellings look wrong, so I tend to avoid writing it, though it's certainly part of the language.