Clogged main outside, toilet and shower wont drain we have septic tank?

if water rises in your shower drain as you flush your toilet, kitchen sink or washing machine, then most definitely your main line is plugged. another posibility is the septic tank is full and needs pumping. you can try and remove the clean out plug off the main line clean outs (if you have one) and this will allow the backed up water to drain outside. otherwise, do call in a plumber to snake out the main line or check the septic tank. it might need pumping out