Pain in the butt...literally

So for the last couple of weeks I have had pain when sitting. Like it feels as though I'm sitting on my tailbone rather than the muscles of the butt. I have this pain regardless of whether I sit on a padded chair, vehicle seat, or a stool. What makes it worse is that at work I'm on restrictions that require me to sit most of my shift, thus creating more pain. I didn't get to ask my OB about this the other day as she had to rush the last portion of my appt to get to a delivery down the hall that had complications all of the sudden. I don't see her again until the 13th when I will be 26wks. I have read that it can be caused by the pelvis shifting to support the baby or sciatica. Anyone else have this issue?