Hi Candace,
I also had bulging membranes at 9mm dilated at 21+6. I am pregnant with twins and am on hospital bedrest. Like yourself, they did not want to put in a cerclage, but they did put in a pessary. You might try asking about that. I'm still constantly worried about my membranes rupturing, but at least with the pessary I felt like we tried something. Additionally, it helps support the weight of my uterus, so I feel less heaviness down there. I don't know if you have contractions, but the midwives in the hospital gave me bryophyllum tablets and told me to take them 5 times a day. Since this was before the 24 week viability, they could not give me any tocolytics. Bryophyllum is a natural drug and they gave it to me in tablets. I just chew two tablets every few hours. If contractions start, they told me to chew 2 tablets every 15 minutes for 1 hour.
I also read online about the polar bear and Trendelenburg positions. I try to put myself in these positions a few times a day. If anything, it takes some pressure off of my back from being in bed all day.
Each day counts! Stay strong!