It is just
possible that some chair or bike seat you are using frequently is too soft or gel-filled. Though this may seem counter-intuitive, what soft seats do is prevent your sitbones from keeping your soft tissues up high enough off the sitting surface to prevent the padding from pressing on your surrounding soft tissues and nerves. Soft foam bike saddles often do cause pain and numbness (they sure did for me!) and depending on their dynamics they might contribute to tailbone area pain.
I'm no doctor, but it couldn't hurt to try a harder sitting surface for part of your day to see if this takes pressure off your sitbone area.
Feel your weight on your two sitbones when you sit on a plain wooden chair leaning forward slightly, and see if that is less painful to your tailbone than sitting on a foamy/gel padded surface that pushes up against all parts of your bottom and girl-parts. Simple enough to test out.
I injured my tailbone on my bike badly two years ago, but it was a major direct hit on the hard saddle nose and there was no wondering what the pain source was from. It took about a year to heal well, and believe me I can so sympathize with your tailbone pain.
