Short cervix and scared

I am 20 weeks and 2 days. I just found out yesterday at my routine ultrasound that my cervix has dilated 3 centimeters. I was rushed to the hospital and I am due for cerclage. I am scared shitless that my baby girl wont make it. The doctor's are no help in reassuring me that everything will be ok. This would be my 3rd child, I have two boys 7 & 3 and both were full term with no problems. I really dont know what to think are do. I've had no signs of anything is wrong. My daughter is moving regularly and has a strong heartbeat . I'm just scared u will lose her.