I haven't been on this forum for a long time, and read this. I havent played that piece in a long time, but I performed it for my senior recital back in 2012.
It is a great piece to put simply; it was one of Beethoven's personal favorites actually. I saw youblosted this almost 2 months ago..some things I can think of to help with performing larger works like this include listening to recordings/watching YouTube videos of others performing this piece. As it is not a Chopin etude in the least bit, the mindset and attitude you approach this piece is much different. Listen to each movement separately and hear what Beethoven is conveying; it is such an organic piece, the LH tremolos in the first movement are like a heartbeat (one of several analogies..kinda cliche but true).
It sounds like you lose some interest due to the length of it; so look at each section separately and how it all fits together (the nice thing about sonata form is that it let's you examine each section within the movements as it's own entity in a way...sorry if it's a bit vague, I havent been on this site in years, need to sleep, but reading this post stuck out to me; this is one of the first Beethoven pieces I fell in love with and performed at different times in my life, so I have so much I can say about this but trying to not overwhelm).
Also, maybe read some background history about the piece; such as this is the only piano sonata he actually gave a name to, and the first one to be published as a single work in an opus (op.13 contains only this one sonata). It's in C minor, Beethoven's favorite key signature (and what Chopin's op.25, no.12 is in as well, another wonderful piece)...there is so much about this piece that is just wonderful, that it is easy to become a bit lost in the journey of performing it. I've given these suggestions because when I have encountered a stumbling block in pieces, I will look at why the composer did it, why it was composed, what value did this piece have, etc. There is so much more than just the notes on the paper and the conventional analysis; it's Beethoven, a composer you can go overboard with (to a certain degree of course...take what I said in context, still make it sound like Beethoven), since...well Beethoven was a revolutionary, and this piece was definitely one of the first to show that.
Sorry if that's a lot, I just have more I can say but it's long already and I'm typing this on a phone, so to put short:
-Listen to recordings (with and without the score)
-Read some history on it (this is a very famous sonata, so it's easy to find material to skim through)
-Practice in small parts to understand it as a whole piece
-It's Beethoven...think big (you sound like you have good technique, so that's good, it's just understanding this larger form and doing it justice)
-And of course, enjoy and have fun playing it; it's great music, what could be better?
I hope that you have become more intimate with this piece from the original post date, and if you are still struggling with it, I hope that some of these tips can help you. Good luck and have fun:)