What now?!

Well, Aunt Flo was due around April 6th, but I think she missed her flight. I've been regular since I was 12, even after a 16wk miscarriage and a d&c. The only thing that changed after those was I haven't had cramps. Those were last May and November respectively. I've take five first response tests since (we aren't ttc avidly, but we're not avoiding pg), and even a blood test that all came back negative. I have POTS, which includes dizziness, nausea, fatigue, and more symptoms very similar to pregnancy, so Aunt Flo is really my only resource. I'm at such a loss of what to do. Has anyone had similar experiences?