Missed period.

I am now on the 3rd day of what should be my period but there has been no sight of it. I've had the cramps and the bloating and my boobs hurt more than when my period would come. I get faintly queezy throughout the day and have hot flashes which makes everything worse. I'm bloated and uncomfortable and I have no idea what's going on. Every pregnancy test is negative and maybe I just don't have enough hcg to generate a positive. But I am now 3 days late for my monthly and am very scared.