Ran water to take shower, tub filling - shut off shower, tub drained slowly. Toilet gurgeled/bubled. Ran water in sink all OK in sink but heard gurgle. Used toliet- flushed-backed up to rim. Plunged. Stayed same but slowly drained on its own. Tub small amount of water - plunged - water came up from drain into tub, plunged some more and cloudy water came up from drain and continued on its own and added to tub, plunged again and now tub is filled with what appears to be toilet related sewerage. Any suggestions how I can fix this "crap"? Smells bad and is not draining out of tub at all and toilet plunge adds to tub. Toilet is in drained state but fills to rim and slow drains when flushed. Toilet and tub side by side, sink across from toilet. Septic system - everyone is clear on only body fluids and tp gets flushed. Initially it seemed like there might be air bubble in pipe but now I'm stuck with a tub full of crappy standing water. Gross! Help!