Blood tests and Pregnancy Tests.

Blaire

got my four positive HPT at 2 days late of AF so I went to the doctor for my first check up and took my urine test which came out negative. I'm now taking a blood test. Did anyone ever take urine test and it was negative but took a blood test and it was positive? I would be around 4 weeks right now, should my HCG show up in my blood test?