Hello, I just recently turned 18 and my nipples have constantly been hard for the past week. I've been reading various posts about the cause for this and has begun to get very scared because they all conclude to the same thing---pregnancy. My boyfriend of 4 years and I have been having sex constantly since the day after I came off my 5-day cycle: august 9th. I am due to start again sometime around September 3rd or 4th. Can you please provide some explanation for this other than pregnancy? When is the earliest I can take an accurate pregnancy test before my next period?