What could this be?

Abigail
Okay my period is regular as I am on the pill, I always get it either the Sunday night, Monday, or a few times on a Tuesday. Well Saturday I had some bleeding like normal red colour of a period (wasn't light pink or dark like old blood) so put a tampon in and then there was no more bleeding since that bit on Saturday. 
I've been cramping like normal and have the normal bloating that I always have right before my period starts, just no period yet. 
Should I be worried?