Help Ladies, When Should I see positive?

My period is due on the eighth, and yesterday I went to the doctors for extreme breast tenderness that has been increasing for over a week. Purple rings on bottom of nipples and increase in breast size. I've also been belching and somewhat nauseous. Light back pain and cramping that has been constant for a few days. She did a blood test and it can back negative! Could it just be to early? My app says my ovulation would have been the 23-25! This would be my first pregnancy. 😁