I'm sorry you were not happy with your care, it seems it's always hit or miss when there are many doctors in a practice.
Since this is my second go around of the cervical issues, I do know that sometimes they are extremely quick, just to check the length, and most of the time the baby isn't even looked at, as long as your anatomy scan and everything else checked out fine. And yes, vaginal u/s can be painful and cause cramping afterwards.
Is this your first? From everything I've experienced and read, it's not standard practice to start progesterone for a first pregnancy unless you have signs of PTL or a really short cervix, but since yours seems stable, I don't think it would warrant progesterone at this point. I know it's tough, but I think there just isn't a way to know if it's helpful at this point with a first pregnancy. All the signs DO point to you being able to carry to term even with you not on it right now.
Also, unless there are concerns about the baby's growth, at least in my experience, I don't receive growth scans at all. With my 1st, I just had an u/s at 6 weeks because I had some bleeding, then the anatomy scan at 20 weeks and that was it. With my second I had the cervical scans until 24 weeks and none after. With this baby I am scheduled for a growth scan around 28 weeks, I think because the baby is measuring somewhat small, but I know it's because I ovulated later than they are calculating, so I'm not too concerned.
I totally get the anxiety. I'm very much the type of person that needs constant reassurance, and every little thing makes me paranoid. However, based on the research and based on the assurances of one of the doctors I saw who I immediately knew knows his stuff, I'm convinced the care I'm getting (and from what it sounds like, you're getting as well) is right in line with everything proven to help at this point. Anything more is just there to "make us feel better" because as the doctor put it, often doing something feels better than doing nothing even if it truly doesn't help.
And I know how hard it is to just wait it out. I've been there once and am there again (I'm 24 weeks today!) I wish there was more I could do to ensure I won't deliver early, but at this point medically, everything IS being done that can be, and the chances are good, but even with all that there's still the chance of going into PTL. Just be sure to watch for any real signs of labor, listen to your body, and enjoy the milestone you have reached and focus on meeting the next one!