I have a 28 day cycle and tested positive the day before I was supposed to start my period. I tested positive again the day after I should have started, because I didn't believe the first one! I recently gave birth to my new baby boy, so the test was correct! However, I know a lot of times you are supposed to wait at least a week after you should have started your period to test more accurately, but for some reason mine showed positive earlier than that. Good luck!