Positive test at home, negative at doctors

I took a pregnancy test last night and it was positive!  I've been nauseous and had swollen breasts all week. Glow says I am 4 weeks and 2 days. I went to the doctor today to confirm with a urine test and it was negative! The nurse said to come back in 2 weeks because my hormones may be low (I technically haven't even missed a period yet). Has this happened to anyone else?  I'm told doctor tests are less sensitive than home tests.  It's my first, so everything is new.