It’d be good if you could make him move around a little, but it does sound like there could be a blockage. The most important thing when a bun gets a blockage is fluids. It’s often not enough to give fluids by mouth, sub q or even intravenous fluids might be needed. 

If it seems like he’s in pain, I think you should take him in. If you have baby gas drops (simethicone), you can give him a ml of those, that can help with gas – gas can build up when a bun has tummy trouble, and if the gas can’t get out, it’s very painful for the bunny and it can develop into a dangerous bloat. If there’s a blockage you can’t give motility drugs (=drugs that make the intestines move) because that can worsen the problem. 

It’s really odd that he’s not peeing either. Have you noticed if he drinks?