So I have. A question for everyone , I am 13 days late getting my peri…

So I have. A question for everyone , I am 13 days late getting my period and I took a home pregnancy test and got blood down and they all day negative, so I’m not sure what is going on , I have been on my birth control for two Months now , idk what I still right now haven’t gotten it . My last period was March 15 and we are almost done with the month of April and I still haven’t gotten it . Need help.