I m having pretty severe lower back pain right at my tailbone. It gets worse when I try to stand up straight. Its happened before but gradually went away after a few days. I haven t injured my back or anything like that. It just starts out of nowhere, it seems. Sometimes it seems like its loosing my bowels, although I m not incontinent. Could you possibly tell me what this is? I m a 31 yr old female, 4 11.5 , and around 180lbs. I ve had a history of back pain since I had an epidural 13 years ago, but its usually more in the center of my spine. What I m experiencing now is completely different and much worse.