If this continues for another week and a half, consider bringing a stool sample in to a vet. If no poop bugs are found, he needs an x-ray to check for a compaction. What he's doing right now is packing more matter behind the un-pooped stool in his body. If he doesn't poop soon, he will need help.
I've read that roundworms can clog intestines. Maybe tapeworms also. Where do they contact such bugs? From veggies grown in dirt. Veggies can be disinfected with chlorine, but I don't know the procedure. Once I pressed the grower from whom I bought my organic greens and veggies, and he carefully admitted he was required by law to soak his produce in chlorinated water, and then rinse them enough to leave the prescribed residual. He said he uses washing machines to do it - LOL, very good idea. I was glad he followed that practice; no rabbit, chicken, or cow poop parasites for me, thank you.