I have a downstairs toilet leaking at the base. Since this has occur, sewage has starting backing up in tubs and sinks. When the washing machine is running, the toilets start bubbling. Any ideas?

You definitely have a clog somewhere downstream of the downstairs toilet. And I am guessing the tubs and sinks that are backing up are upstream of the downstairs toilet. You could try snaking the line yourself, or perhaps you have a cleanout somewhere that you can snake a garden house down and run water down there to push the clog away. If you go this approach, be careful that when you open the cleanout, you don't get water to drain back on you. If doing stuff like this is outside your comfort zone, then perhaps roto-reuter (spelled wrong I think) is your best bet.

Hope this helps