My toilet clogs up and needs plunged every other flushing. It started about 3 weeks ago. Now an odor (like something died) is in the bathroom. It seems to get worse after flushing the toilet. We have a well/septic tank. What could this be?

There is a clog in the line that is only going to get worse the longer you don't attend to it. Suggest you track down the clog in the line.

Do any other drains in the house have a problem and how well does your tub and washing machine drain work/ If everything else is working great then you dohave aclog in the toilet drain. I would start by plunging and then if that did not help go up to a toilet auger.