bleeding? what does this mean?

So I am not supposed to start my period for two weeks... yesterday I started spotting and it was medium to light and would come and stop. Today and last night it started getting heavier to where a panty liner isn't working. I am nervous I was pretty sure the spotting was a sign of implantation bleeding. But now that it's getting heavier and hasn't stopped I am worried. Does this mean I am not pregnant or this is just my period? If so why is it so early?