i have ben told that once you hit the 8th week chance of misscarriage drops to less then 5 percent, i also have had misscarriage in the past and had the same fears, im currently 15 wk preg wit twins and still fear the worst, i purchaced a doppler monitor on amazon to help curb my fears in between doc apt it has been a heaven sent, when you hear your babies heart beat it sooths you.
my dr told me that once they heard the heart beat my risk of miscarriage would drop. Alot of people i know have had miscarriages with their first and then go on to have normal healthy pregnancys. Just try not to stress bc I hear you can also stress the baby. think positive! good luck to you :)
I am not sure of the precentages are but i do know from 1st hand experience it can happen. Just try to relax and i am sure everything will work out fine