There a fatty substance in my stool?

I returned from Peru in December with a case of diarrhea (since this was my 2nd time, I assumed it was a change in my diet). But this time, after taking Imodium A-D, it turned to difficulty passing my bowels. Recently the infrequent bowel movement became very uncomfortable (but not painful). Wednesday and Thursday I took two doses of PHILLIPS Laxative pills and it quickly turned to diarrhea so severe that even drinking water resulted in going to the liquid bowel movement. Again I turned to Imodium A-D and it stopped. Not it has been 5 days and today I passed my first bowel movement, but I was concerned because it contained a liht tan (fatty???) substance througout. I was able to exam a piece that had attached to the tissue while wiping. My diet is mostly canned fish (herring and sardines), canned soup, and canned vegatables. I take multi vitamins, along with a 1000 dose E and D. My girlfriend and I want to have a baby. I am 43yo; black male. What might it be???