I skipped the last 4 pills before placebo due surgery. i started next pack on time and have not had period. is this normal?

Placebo pills: Generally not an issue those placebo pills are simply inert pills. If you haven't gone off cycle you should be fine - the surgery and stress of surgery may have interfered with your normal cycle.

Can be: The stress of the upcoming surgery may have delayed your menses. Just continue on with the new pack as directed. If there is any question, have a pregnancy test done.