Cervix change

Im 31 week pregnant w/twins I was Sent to the hospital a couple weeks ago because the doctor seen that my cervix gotten shorter. The doctor said I went from a 4.0 to a 2.2 within 2weeks. So they gave me all these different meds just in case I deliver early so the babies lungs in brain will be developed. They released me on Saturday and I went to a follow up and they checked my cervix again. Now they saying it's at 3.2. Now two weeks later I get checked again now I'm at a 2.5. Should I be concerned? Did anyone else have a similar situation?