Early Cervical Shortening with Twins

Hello everyone!!! Today I am 24 weeks pregnant with fraternal twins (one boy/one girl). I just had an ultrasound last Thursday and the doctor stated that I was experiencing come cervical shortening already. I just went to get Beta shots two days in a row to speed up the development of my babies’ lungs. He has placed me on moderate bed rest, and I have another ultrasound this upcoming Thursday to see if it has helped at all; if not I will have to be admitted to the hospital, which is difficult because I am still working and have an almost 4 year old at home.

Has anyone else experienced cervical shortening this early? If so, how much longer were you able to carry your babies before they were born?