I am a nineteen year old female, diagnosed with IBS nearly two years ago. For the past couple of days, I have had mild yet uncomfortable muscle spasms in my stomach. These are not constant, but frequent. The spasms are all over my abdomen, not in any one place in particular. Tonight, my BM was a dark brown color with areas that looked darker. Is this the IBS acting up again? Or is this something more serious that I should be concerned about?