Although on the "opposite" end of the digestive tract, I have a friend with achalasia, where (for no reason at all) her lower end of her esophagus went into spasm and just never released. I posted because her symptoms were just like yours, only reversed. She couldn't swallow because her lower esophageal sphincter was always in spasm.

It got worse over 2 years and debilitating after she had her son (they said the hormone change made it worse). She also had botox injections which didn't help and eventually had a "myotomy" where they made an incision and released the spasming muscle. Now, I don't know if that is possible in the rectum, but maybe a consult with a new GI or colorectal surgeon? I'm near Philadelphia and can get you the names of the doctors she saw. It would seem the symptoms are really similar.

I don't know how they can say for sure that your spinal problems aren't causing some of this? Just because they can't see nerve 'compression' on the MRI doesn't mean the nerve isn't irritated. My first signs of disk problems was really bad leg cramps and my hip flexor was in constant spasm. I went on neurontin (after they saw the herniations on MRI) and that helped the spasms tremendously. I had herniations at L4-L5 and L5-S1 and have had 2 microdiskectomies.

Are you having bladder symptoms as well? Because it's the same nerve root that controls your bowels controls your bladder. My spinal surgeon warned me that if I lose control of my bladder or bowels (either by losing them, or by NOT being able to go) then it means the nerve is being compressed and I was supposed to go right to the ER. Have they done an EMG/NCS to determine if the nerve is irritated at all? I would insist on this if it hasn't been done already!