I got a positive pregnancy test when I was 2 weeks pregnant.
That happend to me with my first, the line was so light and hard to tell at first than in less than 2-mins it disappear! Later that week I took another pregnancy test and came out positive! So I check the first pregnancy test (just cause) and the line had came back and it was dark and so clear!!
The best thing you should do is call and make a doctors appointment
Could be that you ovulated earlier then you thought. False negatives are much more common than false positives. Congratulations on your pregnancy! Sounds healthy to me.