need advice please.

Valeria
Ok so I took a pregnancy test 2 days ago and yesterday morning both resulting in faint lines. I called my doctor who ordered the blood test. I got the results and it says 17 mIU/ml> 
I looked online and multiple sights and people have said anything abouve <5mIU/ml is a positive. Shortly after my doctor messages me and tells me it's negative. Should I get a second opinion?