Don't know if pregnant or not help please

Ok lady's so 3 weeks ago I took a pregnancy test and it was positive the next day started bleeding when I went to bathroom to pee quit 2 days later went to doctor told me possible miscarriage but I have been all the symptoms of pregnant and more. I have took 6 more from different brands of pregnancy test and they all say positive but the positive side is really light barley can see it.can someone give me some advice I'm suppose to get a ultrasound on Thursday I'm just so confused.