Short cervix?

Just had my 20 week appointment and baby seems perfect but my cervix is short. The tech told me the cervix is suppose to be at a 3 but I’m at a 2.3. I have to come back to another ultrasound with a specialist in a week and don’t get me wrong I’m beyond happy my baby is good but I’m so scared I’ll go into early birth before she hits 30 weeks. Anyone else out there who has a short cervix? What end up happening or what did the doctor suggest you do?