I suspect there is something caught in the trap way that is causing the problem. Some of the things plumber find are children's toys, toothbrushes, makeup cases, and the list goes on. Sometimes a tool call a "closet auger" will clear the blockage from the top, but other times, the toilet has to be pulled up and the problem attacked from the bottom. I know that will compound your problem since this is the only toilet in the house, so perhaps a plumber would be your quickest way to get back to normal. I'm not a fan of pressure assisted toilets, but that's what you have to deal with.