My toilet has been doing a lot of bubbling and then the shower will back up and toilet won't flush. If shower or laundry is used upstairs it will also back up. Does anyone have any idea??

Pour equal parts of warm water and vinegar in shower drain. Let seat overnight and flush in morning with boiling hot water.

If this does not clear blockage will have to snake it. Can try from shower but may have to go from roof vent. If snaking from shower send in about 10 feet past toilet.

Chuck

My toilet has been doing a lot of bubbling and then the shower will back up and toilet won't flush. If shower or laundry is used upstairs it will also back up. Does anyone have any idea???

If warm water and vinegar didn't remove the blockage then it's time to get out the snake.
Let me explain what's happening and then we'll get to the repair part.
You flush or drain and the discharge hits the clog and bounces back sending a bubble of sewer gas ahead of it, m That's the bubbles that you see. You have a blockage downstream from the shower. Is the shower and toilet a basement installation?'
This can be snaked from several locations.
1) If in the basement there may be a stack cleanout that you can snake from.
2) Pull the toilet and snake from there.
3) Remove the shower drain strainer and snake from there, **OR**
4) Snake from the lavatory roof vent.
Good luck, Tom