Thank you for posting your question here, I will try to answer it to the best of my abilities.
and primolut are fertility
drugs given to ladies who are suffering from irregular menstruation
. That is the reason that you're menstruation started normally after you started taking the pills.
So you just have to avoid having unprotected sex on the days you are ovulating, this is calculated by adding 14 days since your last period, the next 4 days are the days when you ovulate, so dont have sex for those 4 days and if you want to be on the safe side, make it 7 days.
If you aren't ovulating, you cant get pregnant.
I hope this answered your question.