Low hgc levels and still pregnat

I am late by 3 weeks, and still the hpt is coming up negative, also went to the obgyn today and had a blood test done. The dr called me with the results and said my level was less than 1 so there is no way I am pregnant. But I am having alot of symptoms even the sore breasts. Now mind you I have been off my iud for over a year and have always been on time or a few days late even after my first miscarriage. Does or has anyone else had this problem?