Dizziness/almost fainting. Early preg symptom?

I have been experiencing cramping this past week AF isn't due until Sept 4th so it's still to early to detect if I am pregnat.  Today I almost fainted in the post office and it took approx 30mins for the dizziness to go away.  Could this be an early preg symptom?  I went to the doctor a couple hours after and they said everything looks good.  They tested my sugars, did a preg test, an ekg, etc.