I'm 5 days late an I'm in the pill! an my period is always very heavy! basically impossible to just not happen

I have done a test an it's negative, I'm on the pill, so periods are meant to come at a certain time, my period usual takes about a day after starting sugar pill, an it's been 5 I'm going to miss the window as I take the actual pill tomorrow, pregnancy is slim but can't think of any reason I would not have a period also no cramps , I will do another test in a couple of days to be sure because I know it some times need a bit to show up, but for someone who's periods are crazy heavy a would last for 10 days this is very abnormal