Late period and very confused.

My periods are never off. They always arrive on time or early. In August I started my period August 2-8 then it then it came again sooner then expected August 28th-September 3rd. I'm now as of today 9 days late. I took a pregnancy test last night and it looked negative but then a couple hours later there was the very light purple positive line meaning pregnant. So I took another test this morning and it was negative. I'm confused. I've always cramped a week before my period and I'm still 9 days late barely cramping. Sometimes here and there. But I'm confused.