5 days late with negative tests.

So my periods are always on time, like clockwork on time, and right around ovulation time last month my husband and I did the baby dance but only the day before ovulation. I had some very light spotting around two weeks ago maybe the beginning of last week (I cant quite remember exactly when), and I thought I would be getting my period early. But alas, I'm 5 days late today. I've taken 4 tests. 3 pink dye and 1 blue. All negative. I've been having some cramping but in the middle of my belly, not where I usually have it when it's that time. Any ideas what's going on? I was going to give it until Friday and see if I get my period but then before I call my doctor. And tips anyone can give would be appreciated