I have a large lump on my tail bone, it s right at the tip of my butt crack and its rather large, very hard and very painful. It hurts to sit, stand, walk, bend, move. Its painful to the touch and it sends severe pain in my lower back area and down my right leg. It almost feels like its part of my bone, yet it literally feels like I am growing a very painful tail. Any idea of what this could be?