Lubuto,
If you had an external scan, then you wouldn't be expected to see anything this early. Especially, if you have a retroverted uterus.
For instance, a heartbeat can usually be detected by internal scan at 6.5 weeks. With an external scan you would only detect it two weeks later. If you're, ahem, heavier it could be even later!
As for the symptoms, it is absolutely normal for them to die down while you sleep. I go to bed with HUUUUUGE tender boobies, but when I wake up they're almost back to normal.
Asibling, if you're not sure about your ovulation date, try not to worry too much yet. Do you know what the diameter of the gestational sac was?