None of this sounds right. Why did your doctor give you expired pills? While they still may work, that's not really how sample packs of pills are to be used and that's not really helpful of him. Sigh. Did you get instructions on what day to start your pills? Normally, it is started on the first Sunday after your period begins. But then you stopped taking it. I'm confused . . . were you taking it for birth control/ to prevent pregnancy?
You never took it for the whole time or regularly so it wouldn't be working. BUT< you used condoms which as long as they didn't break and were used properly, should prevent pregnancy.
You are likely late because you altered your hormonal balance briefly by adding the pill for a bit. This will throw things off and being late would be a normal reaction.