English, and really school in general can get really boring, and especially coming from a student who isn't an avid English student can find it harder to be motivated by preexisting class work. However, everyone likes a good story. You just might not be able to find it in school. For me, I'm not a particularly avid reader, in fact, at times I really hate reading. Scanning my eyes across a white background with repetitious black characters tires my eyes and my mind out quite a lot, and it's very hard for me to find a book that I'm enthralled in.
However, I far prefer interactive media such as video games and looking into them deeply. Movies and song lyrics are also great analysis material as well. Adjusting yourself to being more perceptive when watching movies or playing video games and asking "why did the creators do this?" or "why is this a repeated symbol?" and then coming to an epiphany is a great feeling, and far better than writing some essay on a book you don't care about and already discussed to death by the teacher and upper-level students.
So I suggest to you to find motivation is to find a medium in which you enjoy interacting with Literature. It is not by any means limited to what school offers or what books offer, it goes way further. And practising analysis on things other than books, or even things not as complex as some books isn't a waste of time whatsoever. I've written great analyses just out of my own free will, which had nothing to do with books or school. It was purely just for fun and my own learning.
Oh, and you said that you average A to A+ SACs, which I can't judge whether they were "flukes" as you put it or not, but also be careful to not get doubtful of yourself. Of course be realistic, and if you think there is going to be an actual downfall in your grades, try not to wallow into treacherous pessimism. Literature is a lot of fun if you find a good story.
Hope this helps.