Confused and need answers maybe something similar has happened

So I recently noticed I haven’t been feeling well and was getting symptoms the same from my last pregnancy and was getting very faint positives (ended up having a ectopic pregnancy and having miscarriage) but doctors couldn’t detect hcg with urine test only blood test. But once again I’m taking test and get faint lines. So I made a doctors appointment and they say there urine test is negative. Do you see a line? And if so how come I’m getting them on my test but they aren’t on theirs?