Pregnant or period?

Ok, so I've done a lot of researching online and I'm coming up with every situation poossible. So I started my period today, something wasn't right right off the get go. It was so heavy (3 super tampons in 5 hours) at about the 3rd hour (2nd tampon) I had 2 pinkish, stringy, mucus clots.. Scared me thinking I was miscarrying. I'm not (that I know of) pregnant, but this has never happened to me. Now after all that, my period is slowing down to a very light flow. Granted this is only day one of my period, but does anyone know what this could be, or if I should be concerned?