With my second baby, I had a negative pregnancy test, and the child is 8 years old now, and I still say he's awkward!
I got the test done when I was a couple of days late, and I knew I was pregnant, so when it was negative I waited 2 weeks before doing another, which was then postitive.
If you are pregnant, it would be a bit early for the heartburn and nausea, although you would have tender breasts and going to the toilet quite early.
Let us know how you get on.