I sincerely hope what Thistle has isn't Crohn's. Crohn's is a damn miserable disorder, with sufferers quickly degenerating to complete misery. Lifespan usually isn't good, as repeated surgeries remove more and more of the digestive tract.

Without more detailed symptoms I couldn't begin to guess at a proper diagnosis, but even then I'm just a genius and not a medical professional (though the book-learning is similar). I definitely would advise consulting a doctor, particularly a GI specialist (seriously, don't trust a GP or Internal Med with this).