Cervical Shortening 16 weeks

Hi ladies! I am 16+3 today and spent all morning in the ER with severe cramps and nausea from the pain. My vagina has felt like it's throbbing all day and several days this week when I wipe after peeing, there's copious amounts of mucous discharge. No bleeding or spotting. 3 ER nurses could not find a heartbeat with Doppler so we had to do an ultrasound. I found out I have anterior placenta (which makes since why they can never find the heart beat) and my cervix only measured at 2.4 cm. The did not express to me any cause for concern and sent me home, stating I can go back to work tomorrow. However upon my own research, I've found 2.4 cm is not a good measurement and I should be at least 4-5 cm at 16 weeks and only down to 3 cm or less after 35 weeks!!! I called my OBGYN immediately and he cannot get me in for a full examination until Monday morning, telling me to stay on bedrest and no sex. I've read that any cervix measurement below 2.5 cm should have a cerclage along with continued bed and pelvic rest, biweekly cervical checks monitoring for preterm labor, and possible progesterone suppository or injections. Has anyone else experienced cervical shortening to this extent this early?? How was it treated? Did you deliver early? We're you high risk? And how do I NOT worry myself sick!?