Crampy?

I don't get any cramps/moods/cravings until the day Before my period comes. I don't get it until this Friday (periods come on time like clockwork for me) but the last 4 days or so i have been crampy all day every day, I get the shakes and feel so tired even with going to bed a little earlier. Does anyone know what could be causing this, I'm exhausted and tired of the sharp pain/cramps every day all day. The cramps range from light to painful all day.