How to get back on track after falling behind
I want to give you one piece of advice which I think is very important:  Sleep more.

If you don't get enough sleep, your brain won't work as well and so it will take you longer to understand things.  You will be able to work much more efficiently with enough sleep.  Also, your brain does a lot of important work during sleep, helping reinforce connections made during the day etc.  So the time spent sleeping is not at all a 'waste of time' as far as your study is concerned.

Try not to view sleep as something optional that you can leave out if you don't have time.  Have a go at sleeping at least six hours every night for a couple of weeks (I need at least eight most nights, myself, but six would be a good start at least) and see if you feel a lot more on top of things after that!

In my Honours year I found that it was hard to get to sleep if I had been doing maths within the last two hours before going to bed, so I made a rule that I had to stop doing maths at 10pm every night.  I mostly stuck to it, and it worked very well.

Also, I'd like to offer some encouragement that having to work this hard now doesn't mean you couldn't do a PhD or continue in academia if you wanted to.  I am now doing my second postdoc, and have never worked as hard as I did in my Honours year (that's like the first year of a two-year Masters).