Today I found a yellowish string in my stool and am very concerned. It was not segmented, and was about 4 inches long and a half to one milimeter thick... … Very worried about this, is it like a parasite or something ? I m on antibiotics , and also have been ill with what seems to be a cold , so headaches have been normal to my strain of colds. I ve had abdominal pains on the right side of my body, in the same place and my hands shaky, which isn t normal. The string was stretchy.