possible miscarriage??? I'm so confused

I took 2 pergancy test both with faint lines in the positive so I had my doctor order me a blood test and my hcg was 17mIU/ml>. Then she messaged me "your pregnancy test was negative" isn't anything over 5 a positive? She gave me no explanation. Does this mean I'm going to have a miscarriage? I'm 3 days late with my period. I had very light spotting a couple of days ago but then it went away. Im so anxious.