Hi Kaust, there are a variety of reasons you maybe fatiqued or feel fatiqued with IBS. An importnat chemical in IBS is also associated with sleep and mood. Serotonin.However, muscle tension, dealing with a chronic illness, sleep patterns and other things can result in feeling this way perhaps and it seems to be pretty common, I know I felt tired a lot for sure.You might try these ten relaxation techniques everyday as it can help to boost how you feel, by energizing the body and working on some of the different chemical regulation of the body. http://www.med.unc.edu/medicine/fgidc/relax.htm