Greetings! When you say say "I used to work" it can be inferred that you don't anymore, whilst if you say "I worked" it means you worked before, whether you work now is unsure to us. Hope this helped!

Used to also implies that you did something over a period of time or habitually. I can say 'I worked this morning', i.e., referring to one time I did it. I can't say 'I used to work this morning'

When you say "(Subject) used to work …", you are implying that the subject was habitually doing that action in the past. If you are familiar with European verb tenses, this is one of the imperfect equivalents. The second (I worked) was definitely done in the past at a particular time. This is the preterite or perfect past tense in other European languages.

I used to work....is a action your doing it daily e.g I used to go to the bakery to buy breads every day

I always had to wear fashionable (dresses)clothes when I used to worked.