Heartbroken.....

Just found out both of my sisters are expecting......husband and I have been TTC for a year now, had my 2nd miscarriage in May, my mother said maybe I wasn't prepared and I shouldn't doubt God's plan for us. But one of my sister doesn't even believe in God and my other sister has so many problems w her husband and they're always asking mom to watch their other 2 kids because they say it's too hard to take care of THEIR children.....but I'm the one who "maybe" wasn't ready??? I just don't understand why this happens.....Why can't I keep my babies? Am I not praying enough? Are we BDing on the wrong days? What am I doing wrong? So many questions, so much pain and confusion....