Cervix length

I had an appt with a high risk dr yesterday who told me my cervix was only measuring 2.9 cm. I had a LEEP done a few years ago and knew my cervix was shorter but didn't know it was that short. About 2 1/2 weeks ago my cervix was measuring between 4.5 and 5cm. I am currently 19 weeks 4 days. Has anyone else had experience with this? I'm trying not to stress but have been researching and it's not helping.