Every following month my wife’s periods get postponed by atleast 2-3 days. This has been happening for about 3-4 months now. Because of this we are unable to identify her safe period for unprotected intercourse. Is this normal and what is the cause? She is not on any birth control measure. Are low dose contraceptive pills really safe for having unprotected intercourse around 4 times a week ? Are home pregnancy test kits 100% reliable ? When should they be used for accurate result ? Which one do you recommend ?