False Positive?

I took a test when I was only 2 weeks along, so it had to be right after conception, and I got a POSITIVE! Then, I took another one the next day and it was negative. I was going to wait until I actually missed my period to take another one. I feel like I'm having symptoms of pregnancy such as sore breast, fatigue, headaches, and a little nausea. Could my test have been a false positive? I'm trying not to get too excited. I go to the dr in a week.