Miscarriage

Pee stick lit up like the fourth of July with a positive at just 2 weeks along. Ultrasound at 5 weeks because based on period they thought I was 8 weeks. After the ultrasound began spotting. Spotting began with light brown bleeding. Friday night went to ER was getting blood clots and bright red blood. Levels were 21539. Good right? They told me to come back in 3 days to make sure they were going up and not down. They were suppose to double. Increase by 50 percent. I only increased by 4 percent. He said I'm miscarrying. 5 percent chance my baby will make it. Second miscarriage. Why can't I carry a child? Why can't I get something that I have been trying for for 6 years?