I have overcome some bad constipation problems by getting a juicer and juicing Granny Smith apples. I really swear by this and believe it is just about impossible for anyone to be constipated and drinking this two or three times a day at the same time. There's a world of difference between fresh and bottled apple juice. Fresh juice won't cause the cramps, diarrhea, and spasms that bottled juice can (and usually does). I'm really not sure what makes the difference is here, but there definitely is a big one. What you want is just-juiced apples where the juice is bright green. You'll notice the juice starts to turn brown almost instantly – don't let it sit before you drink it. Once it oxidizes and browns that's when it will start causing the cramps and such.
Do not use store bought juice, it does not work and causes big problems. Don't use other apples; they are not even twenty percent as effective as the green.
If you haven't had a thorough GI workup, there is a new process just recently available called capsule endoscopy. You swallow a large capsule that has a camera inside and the docs can see nearly the whole GI tract. It is a very exciting break through and they are helping people that they could not help before.
The only other thing I could recommend are the Hypno CDs - they really have helped many many people who were ready to give up after trying everything else.
By the way, you need to drink this juice on an empty stomach (don't be afraid – it's NOT like drinking bottled juice at all) and at least two to three times a day.