How early have you tested positive?

Natalie
I took a test a few days ago when I was only 2 days late for my period and I would only be about 2 weeks pregnant (fingers crossed). It tested negative. I'm now 4 days late. Ended up cancelling my dental appt just to be on the safe side. 
Has anyone else ever tried to take a test really early on and tested negative, but later tested again and was pregnant?