I have seen the following quoted portion in a website(beingtheparent.com/unwanted-72-uses-side-effects-precautions).
"A very common side effect of taking Unwanted 72 is significant alteration in periods – they can either be early or be delayed. Most women will experience withdrawal bleeding at the scheduled or expected dates, while some may get menses within 5 days. If you get periods earlier then expected, you can be assured that pregnancy has not taken place, but in case of delay in periods, it is best to take a pregnancy test one week over the expected date. This is largely a rare occurrence. However, if bleeding does not happen within 7 days of expected date or 3 weeks after taking Unwanted 72 merits a medical consultation to rule out chances of pregnancy"
I suggest that you may consult a qualified gynaecologist and use such tabs and pills. When you do that you can also get all your doubts cleared. If prescribed medicines have a leaflet with them for user awareness, read them and understand about the side effects etc if any before taking them and consult doctor on any doubts.