thinning cervix

21 week Dr visit today to find out gender. My happiness turned into pure terror as I was told my cervix is already 50% thinned. Dr is prescribing me a progesterone suppository to take for a week and then recheck my cervix with another vaginal ultrasound. If it shows not to help I will be seeing a high risk pregnancy Dr as well as discussing a surgery to insert stitches. Very upset, no issues with my last pregnancy at all which seemed to confuse my drs as to why I am going through it this time around. Have any of you experienced this?