I have an ache in my middle lower back that is constant. I really feel it when I bend backwards (as though I were going to go into a yoga bridge pose). I've been experiencing it for two months now and it won't go away. I also feel numbness and pain in my tailbone area going down to my buttocks. I feel less sensation than before when I pass gas or have a bowel movement. What could this be attributed to? Should I be alarmed?