If you are not sure you will not have sex on all of the days you can get pregnant, use another method of birth control in addition to fertility awareness-based methods. If you want to avoid hormones, you can use condoms (male or female), a diaphragm or cervical cap with spermicide, or the sponge.
Still not working? If you are having trouble with the fertility awareness-based methods and want a non-hormonal method, consider the ParaGard IUD. It is non-hormonal and does not require a lot of work.
Try a different method: IUD
References:
- Society of Obstetricians and Gynaecologists of Canada. (2015). Canadian Contraception Consensus Chapter 4: Natural Family Planning. JOGC Journal of Obstetrics and Gynaecology Canada. Retrieved from https://www.jogc.com/article/S1701-2163(16)39375-6/pdf