Stairs to the bottom floor

At 2:30am, unable to sleep, I lie on my back and place my hands on my heart and my stomach. My mind turns inward to examine the space inside of my torso. It seems empty. Especially the space between my lowest rib and my hip on the right side. I search deeper there, as my lower rib extends out into a metal staircase descending into a pentagonal cement shaft. The stairs seem to descend without end. It is dark and I am fearful to go any deeper. I imagine the end, very far below, as nothing more than a cement floor. No door, and nothing else exciting, just a flat and cold cement floor where the staircase ends. And the shaft would start to fill with water, so that I would have to ascend the stairs, or float with the water back to the top, or stay there at the bottom and drown.