I've been on birth control for 10 months now however, my pharmacist was unable to refill my prescription on time since they had refill an emergency three months prior. I should have started my new pack on 4/7/17 (after having my period) but did not start it till 4/14/17. My husband and I had sex while on one of my fertile days but I still started my new pack. Long story short, I have not started my period yet and am behind 31 days already (negative pregnancy test) is this normal?