I was pregnant and had no idea and was having very bad migraines that left me unable to see. I went to the ER almost every day for several weeks. They did an HPT when I was 6wks and it was negative. Again at 8wks it was negative. It was not until I was 10wks that the HPT in the ER came up positive. They did a blood test and my HCG was over 200,000. They said that sometimes the HCG is not as potent in urine in some women.