Spotting or period??

So my period has always been light and irregular. There are times that my period blood can fit into a pantie liner. So I took Plan B on June 7 and I started to experience some spotting on June 13. The spotting got heavier as days but was never as heavy as the period. This is the 5th day now and my period is not due until July. So am I getting my period early or is it just spotting? I took a pregnancy test yesterday and it was negative