3/4 days late + long haul flight

Lucy
TTC for about 6 months now and my AF is usually regular, in fact, it came 2 days early last month. It's odd for me that it should be late at all this month. 
We did fly to NZ on 20th Feb, which im pretty sure was after ovulation, but I can't be sure. I was quite ill after the flight and have had very slight symptoms which I attributed to jet lag.
What are your thoughts ladies, should I go and buy a pregnancy test or is the flight just messing with my cycle?