I too had lots of abdominal pain along with pain in the back, found out that i had gallstones and had to have my gallbladder removed. Be careful though, if it is gallstones, see if you can get them lasered out instead of gallbladder being removed, have had bathroom problems and bad stomach ever since. Good luck, let us know what you find out.
I have IBS and I always have lower back pain from mild to severe. Massages and hot baths help and getting rid of gas.
I have abdominal pain, at times very intense pain down both sides, and my lower back hurts much of the time, extending from low low back to upper part of legs.