Intermittant lower back pain and gas

I have been having trouble getting my problem diagnosed. Maybe someone here has had the same symptoms. I have been having excruciating lower back pain that lasts no more than 15 minutes at a time. Often it is accompanied by gas. This will happen 2 or 3 times a day for a few days to a couple of weeks, then I could go weeks without any pain, or a day here and there. I had my gallbladder removed over 10 years ago and I also have endometriosis. My gyne does not think this is endo related and had me have a colonoscopy to rule anything else out. That came out clean...no pun intended;)

I have tried to tie it to when or what I eat, but it appears to be totally random.

Any suggestions would be appreciated.

Thanks!