I dont understand why

This past Monday, I took a pregnancy test and got a positive. I was happy but very scared at this was my 5rh pregnancy, 4th in the last year and a half. I have 1 daughter with my ex husband and have been trying to give her a sibling with my bf. Every one of those pregnancies have ended in miscarriage and apparently this one is no different. I woke up this morning at 3 am and noticed a has bleeding. Then, I started cramping, just like before. I now have 4 angel babies and I'm so depressed. We think we know why this is happening but have yet to have a clear conformation. My bf has a genetic disorder that will allow me to get pregnant but won't let of child live past 8 weeks gestation. But why can't at least 1 live. I can't handle this. When will I get the baby I so desperately want and need? When will this be easier? Why can't my baby live?