WHY IS MY PERIOD BLOOD BROWN

So last night u got my period and when I woke up this morning it was completely brown/black blood with no traces of red at all. Now the flow is gone and there's no more blood coming out. My period was 3 days late and I'm wondering if this is normal. I looked it up and it said I could be pregnant and im really scared. Also, I did have light spotting during ovulation with hints of pink if that helps. I think it was ovulation spotting but I'm not sure. So is all of this normal? Btw, my period are usually regular so all of these things haven't happened to me before