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i agree with StarQueen- checking in with the doctor to get a colonoscopy would be helpful. Regardless, it will make sense to monitor your diet and perhaps change it if symtoms improve. this can require patience. I would try eliminating dairy and see if the pain and the gas improve- dairy intolerance can cause many of the symptoms you are explaining. Note, that eating a diet high in fiber is really important- try introducing high fiber veggies and beans into the diet slowly. it takes some time to build up the enzymes to digest them.
if you do end up getting a colonoscopy, vist my article on how to prepare for one: http://www.wikihealth.com/How_to_prepare_for_a_colonoscopy
Your pain sounds like it is the descending colon. The large intestine begins in the lower right side of the body and comes upward just along the side of the body. This is called the ascending colon. It then crosses across the width of the body from the right to left sides. This is called the transverse colon, then moves downward toward the rectum. These are the descending colon and the rectum. Food that enters the large intestine is referred to as fecal matter. As it moves up the ascending colon and through the transverse colon, it removes and replaces water in the fecal matter until it has the consistancy you see in the toilet. If the body pushes too much water into the colon, you may have anything from diarrhea to "soft" stools. If it takes out too much water, you will see firm to rock hard stools. The amount of water exchanged depends on the amout of water available in the body. You will need to review the amount of water you consume daily. If gass is accumulating in the colon, it could come from many sources as well. If you are okay with water and food, then consider a colonoscopy to check your colon out just to make sure everything is okay.