M.R.
You won't experience any symptoms until implantation, which is typically 6 days after fertilization. If you have a general idea of when you ovulated (since you used a predictor), you can count forward approximately 6 days to determine implantation. This is all under the assumption that an egg was present, fertilization occurred, the cell underwent the correct number of divisions, etc. You won't experience any symptoms until implantation because until the blastocyst (fertilized egg that turns into a blobby clump of cells) lands on the uterine wall and establishes a connection, your body isn't being commanded to make changes to support and establish a human being.
The nausea could be a sign of increased hormone production. The cramping could be a sign of implantation. However, I doubt the tail bone pressure factors in since there isn't any massive uterine growth going on so early. Of course, the pressure could be related to the cramping. For me, my pregnancy signs were breast tenderness (which made me think I was getting my period) and extreme exhaustion...I mean, wanting to go to sleep for the night at 6:30! It's different for every woman, and many women have different pre-preg symptoms with each of their children.
You could try taking a pregnancy test 7-8 days after supposed ovulation. However, you should understand that your body may not have cranked out enough hormone to register. I know it is hard to be patient, but try waiting until two weeks after the ovulation and see what you get. Buy a pregnancy test that has two in a package - take one early and retest later!