Is this possible?!

Dani

Hi ladies! I had a positive pregnancy test the day of my expected period so I made a doctors appointment 6 days after my period was late. All my clearblue tests were negative after my FRER digital was positive. The doctors urine sample was negative but they did an HCG blood test. Is it possible for the urine test to be negative but the blood test to be positive almost a week after my period was late? Has anyone experienced this? (Please comment)