Toilets, Sinks, Showers, Tubs and Disposals - Bathroom plumbing issues

I own a house that was built in the late 1940's in northern Louisiana. I started having problems with the toilet not flushing well a few weeks ago, and it has since gotten progressively worse. I believe there is a clog in the line that provides drainage for all the plumbing in the bathroom, because now when the toilet is flushed, it will drain into the tub. It used to be that this would only happen when the toilet was flushed frequently, or after someone took a shower or a bath, and then it would slowly drain out of the tub after it had backed up. Now, it won't even drain at all. I am also having similar drainage issues with the sinks, although the toilet thankfully doesn't back up into them. I don't really know much at all about plumbing, but I can't really afford a plumber right now. I'm assuming that this is beyond a little bit of drano? Any tips? Do I REALLY need a plumber? Thanks!

DanielSchaffer, Welcome to the DIY Forums.
You can rent a power snake and remove the toilet to provide access to the bathroom plumbing. Usually, when a toilet has a clog in the line, it involves solids wrapped in paper. A small snake will sometimes go through the paper and not dislodge the clog. If it were just the toilet backing up, I would tend to think it was something in the trap but it seems to be further down the line. You mentioned Drano. Caustic drain cleaners eat a hole in the clog and then run down the pipes leaving a partil clog to start the process all over again. If you are going to try a drain cleaner, try an enzyme drain cleaner such as Draincare. Enzyme cleaners cling to organic clogs and "eat" them. Safe for septic systems. Takes overnight but does work. Follow label directions including using hot water. Good luck.