We have a 33 yr old house that we've owned for 8 years. No plumbing problems or changes in that time. We have two and one-half baths, with the half bath downstairs. Concrete slab foundation. Last week, the downstairs toilet started overflowing when water was run anywhere in the house. We've used a 75' power auger on the two clean-outs on the house, but no improvement. We pulled downstairs toilet to use auger from below, but it just goes up the pipe to the upstairs bathroom. We don't have a septic tank or a clean out/access in the yard.

What is the next step for us?