I'm on the 21 day pill and on my app it tells me what days to take it and not and my last period was on the 24-29 Dec and now it is telling me I should have started my period yesterday and I'm getting worried as it normally starts the day it says it's going to. I'm confused to why it's changing the days as my doctor said it wouldn't and I'm worried because I have been having unprotected sex on my "break days". I have also had sex before my period so I'm just worried can you help me out?