Temp. Changes and weird period

I had the weirdest period...I was due on the 30th...it started out like implantation spotting...then a little more. Medium to light flow more like spotting, and no clots (eeiiuuu) and the weirdest thing, it lasted 3 days only.. cramps a week before my period(this never happens to me). My regular periods start out spotting and then heavy flow...really bad cramps in the 2 or 3rd day and it lasts 7 or more days wirh heavy flow. Also, my temperature went from 97.6 to 98.2... any opinions ladies? Took a pregnancy test and came back negative.