I just started having a problem with my toilet/shower. If I fill the tub with water to give kids a bath, or if I take a shower right after my wife, the toilet next to the tub bubbles, a lot. I don't hear anything in the sinks next to the toilet. And when that happens, the toilet will not flush for a little while. I was thinking it was a backed up septic, but I was pumped about 3 yrs. Ago.