Becky,
Given your complications, there may be things that only a doctor can manage, but my understanding is that it is VERY normal for the cervix not to efface until you are in active labor. I swear, I feel like doctors will use anything to try to get women on that pitocin drip or on the C-section table.
If you lost your mucous plug, then your cervix seems to be doing its thing. Just try to relax. If your cervix doesn't do its job during the labor, you'll have plenty of time to notice and change plans to a C. And doctors don't know squat about sizing babies in utero. They are often a pound or more off. And I know several women who have delivered babies more than 10 pounds naturally, and they are not large women. The only way to size a pelvis is to have a baby come out of it (or not, as the case may be). Most women are sized correctly for the babies they grow. And in any case, it's easy to change to the C *during* labor, but once you do it, you can't go back to natural!