4days late

So i am 4 days late in my period. I took a pregnancy the day before yesterday and another one yesterday and they both came back negative. I am on the Paraguard IUD. So my periods have been consistently on the dot every month. And normally i know when I’m about to get my period but this time i just haven’t.. so that being said today (day 4) i woke up feeling super dizzy and lightheaded. I’m definitely not trying to get pregnant AT ALL. I am done having kids but this is weird..

So i be worried?