I agree also false positives do happen. You have never had a risk I need to tell you this get educated on stds and hiv so when you do start having sex you will take precautions when doing so. GOODLUCK
i agree with mike.
taking into consideration that you have never had sex, no drugs, no risk...then i think it is safe to say that your first test was a false positive as mike stated.
Aslam,
It seems that your initial test generated a false positive,ELISA's some times does yield false positives, if you tested negative the very next day, it's a great indication that you are never really infected at the first place because false positives are definitely common with the ELISA's but not the False negative.
I would suggest you to see a medical professional who could help you in guiding you through the right tests to eliminate the doubt completely. Ideally, you should have been administered with a Western Blot test to confirm that you yielded a false positive.
Good Luck
Mike