What Causes Tight Sensation On The Left Side Of The Abdomen?

For the past 72 hours, I have been experiencing an unusually high amount of bowel sounds and tightness on the left side of my abdomen, right between my navel and rib cage. There is mild pain when I need to defecate that grows in severity over the course of a minute or two. It has been intense enough to make me question whether or not to go to work (for someone who hasn t called in to work at any job I ve had in over three years, this was a big deal). But then, when I go to defecate, the amount of feces in no way justifies the severity of the pressure and pain (a few thin, light-brown tendrils, no blood so far--not the usual dark brown, log-like turds). And even getting those to come out takes 10 - 30 seconds of sitting and waiting (no straining). This is also abnormal for me since I usually just go without any problems or waiting. I haven t had any major diet changes. I m a 30-year-old, African-American female with a family history of diabetes, stroke, chemical dependency, and heart disease (top 4), who weights nearly 295 pounds at 5-foot-7. I had an IUD (Mirena) implanted 13 days ago and am currently menstruating moderately (lighter than the dysmenorrhea I m used to). I have iron-deficiency anemia and carpal tunnel syndrome. I work at a newspaper company loading 5 - 10-pound bundles of advertising inserts into machines about as tall as my shoulders.