What Causes Delay In Period After Changing Birth Control From Microgynon To Loestrin 20?

Hi, I am 22years old and have been on the pill for about 6years. I changed my pill in the summer from Microgynon to Loestrin 20. Generally my periods have been fairly regular however this month I never started, at all... not even spotting. I took a pregnancy test to make sure and it was negative. I flew 2 days before taking the last pill in the pack and because it was a night flight i also forgot to take that pill however took it when i remembered the following day. Could this have affected the it? Should I be worried? Shall i wait until next month and see if it happens again? and Shall I start taking my next pack of pills?Thanks