Sometimes lower back pain can be kidney stones. I even know someone who had similar symptoms as yours who actually had appendicitis - because of the unusual location, the doctors were clueless until it almost burst. Every person is different, so it is impossible to know the exact problem from the description of a few symptoms.
I would start with a colon cleanse.
It might be good for you to go on a juice fast for a few days.
These things will clear the way for the toxins to exit when you do your next cleanses.
After you have a few days of the Colon Cleanse under your belt, try a kidney cleanse, liver/gallbladder cleanse and parasite cleanse - the order you do these in should correlate to what probability you think these could be contributing to your problem.
Chanca Piedra is an herb that can dissolve kidney stones.
If you suspect appedicitis, you may want to take some olive leaf extract, twice a day for about 30 days, drink Pau D'arco tea, take some good probiotics, and eat plenty of artichokes, asparagus, garlic, and onions (these foods feed the healthy bacteria in your body). The appendix is the organ that helps your body incubate healthy bacteria (contrary to the medical belief that it is useless). You don't want the doctors to try to remove it unless it's an emergency.