Positive frer but negative urine at doctor?

AF is due today. No sign of her. I had just a little bit of brown spotting yesterday, only like twice. I have been having dull cramps in my lower back. I took this test today and looks pos to me! So I immediately went on to my family doc... she said their urine test was negative!! I showed her my frer, she said that’s definitely a line, and to just wait a few more days and test again.. what do y’all think? Are doctors urine tests not as sensitive as frer??