I think that looks like some pics I have seen of parts of a tapeworm. There is also a kind of parasite that looks kind of like a nut & is hard. That looks like maybe the same thing. Since you have some that look alike it sounds like parasites. Digested food doesn't come out in matching kinds.
In a way it may not matter what kind of parasite it is, though we all are curious to know those things. The main thing is, as someone said, above, you need to get busy cleansing. The chances are not good that it is the only "critter" in there.
As far as seeing a doctor to get rid of them, I think most are clueless on that topic or they know may about a few of them only. Many of us have gotten negative test results for parasites then seen tons in the toilet when we started just doing the standard otc things to kill them. That tells you the state of the "art" on parasites in standard medicine.
Save your money. If you use the standard paracides & zappers, and do low (2 cups at a time with acidophilus yogurt the last time) you will see them coming out in the toilet. That is the best "test" to show they are dying, mho.