Q. Are changes in bowel habits and varying stool consistency pointing towards IBS?

Hi doctor,

I am a 37 year old male. My only diagnosed health issues are mild hypertension and acid reflux. I take medicines for both. Over the past three months, I had been experiencing a change in bowel habits. It starts with normal stool, then a bout of constipation or hard stool and then loose or thin stool then normal again and it keeps changing. Sometimes, the abnormal stool would occur with abdominal discomfort and cramping. I had a normal colonoscopy about four years ago. I also recently had a normal KUB x-ray to check for any significant blockages.My gastroenterologist did not seem to be concerned with these symptoms and suggested a fiber supplement. I tried Benefiber (wheat dextrin) and that did not have much of an effect. About one week ago, I switched to Metamucil (psyllium) and within a few days of starting, I passed a large amount of stool. Since then, I have felt much better. There is no cramping and I have been passing stool about three to five times a day. 

The last piece of the puzzle, though, for me, is that the stool I have passed over the past week has been of varying size and consistency. Some stool looks normal and in between, there are thin, firm and unusual rubbery strands formed together. I am concerned about these unusual stools and I have attached a photo. Is what I am describing consistent with IBS? Or could this be a parasite? Should I be concerned about this more serious?