What Does Pain In The Tailbone During Pregnancy Indicate?

I’m currently 29 weeks pregnant, and about a week and a half ago I started to notice tailbone pain. It wasn’t too bad at first, I just thought it was from my ligaments loosening from relaxin. But now, it hurts so much worse. It hurts sitting, standing, walking, all the time. It’s also not right on my tailbone anymore. I received an Rhogam injection last week in my right buttocks cheek, and after that I noticed a hard bump under my skin on the right buttocks cheek right next to the crack, almost in between my buttocks right under the tailbone (not on my tailbone at all). It’s not the injection site. There’s no redness and no swelling really, and also there’s no drainage or any signs that it’s there besides the really intense aching and occasional stinging (like someone is poking it with a needle). Tylenol helps a bit. I tried an Epsom salt bath and that didn’t help at all. What could it be?