Negative tests.

So I have pretty regular cycles. They always start a couple days earlier than what my calendar says. My period is supposed to be over today but it never even started. I had what I belive to be implantation cramping between the 14th and 17th. I'm having no feeling of aunt flo showing up. I took a dollar tree test this morning using first morning pee and it was negative. I took two yesterday afternoon and same. Both negative. I've never had a period just completely miss it's time frame before. Any advise would be so awesome as I just am dying over here.