So confused

I got very faint lines around 3 weeks/11 dpo. I am now 5 weeks, 2 days. After I got the definite line I stopped testing. 4 days ago I started experiencing very light bleeding accompanied by cramps-- still going on now and blood only present when I wipe after using the bathroom.

I went to my obgyn today and nothing was seen on the ultrasound and she said that the urine pregnancy test came back very light-- which indicates low HCG levels. Got blood work done, going back in two days to find out more. She thinks I may be miscarrying.

BUT--- I took this test and the HCG line showed up instantly and is SO dark. Took this at 8pm. If my HCG were low wouldn't it be lighter? I know I will have answers soon.. it just doesn't make sense to me!