How sensitive is Drs urine test??

Latasha • Had ectopic pregnancy of march 2010, had 3 miscarriages December 2012-march 2013 with drs help. Now pg w/rainbow baby!
So when I went to the urine test at the Drs office they said it was faint & I was thinking it was because I had drank too much before doing it. I just took a first response & its a very strong positive. I'm 4 weeks 4 days according to dr but my ultrasound is on January 9th when I'll be 6 weeks 3 days. I'm excited but nervous as well. 
Here is the test from tonight. The test line came up as soon as the test was laid down.