Thanks for posting your question here, I will try to answer it to the best of my abilities.
pills dont work for you, why not just calculate the days when you ovulate? These are the danger days when you can get pregnant.
This is how you calculate it - count 14 days from your last period, the next 4 days after that are the danger day, i.e the days you are ovulating.
So just to be on the safe side, for 7 days instead of the 4 I mentioned avoid intercourse and you should be okay.
I hope this answered your question.