You are taking OVRAL-G/AVIANE/DEMULEN for long time and these are all contraceptive
pill for preventing unwanted pregnancy
with effectiveness more than 99% if taken in regular manner.
If you want to conceive,then you have to stop taking those OCP
from new cycle and have to do unprotected sex around ovulation time. Ovulation occurs approx 14 days prior to due date.
An other thing,if you vomit those pill and using for contraception
,then need some extra protection with condom/emergency pill etc. Pill with irregular taking has high failure rate.
Do a home pregnancy test with urine for hcg
after 1 wk of missed due date to exclude/confirm pregnancy.Be well.