I am so scared

So yesterday I had an ultrasound and my doctor told me that my Cervix has shorten to 2.6 from a 4.5 last month. My last appointment she told me my Cervix was great and this one it’s shorten. I don’t understand how it shorten so much in that little bit of time. What does this mean that it is shorten. Will that mean I will have my baby early? Does this mean I have Cervical incompetence I’m like freaking out.

They put me on bed rest. Should I get a second opinion on this because it just seems so unreal please help has anyone experienced this.