First, don't be discouraged. I've personally helped many students go from sub-500 to well into the mid 500s. There's a post on MCAT Reddit right now from a guy who went 488 to 520?...or something close to that. You might ask him what he found most helpful. Personally, I believe the MCAT is more simple than people make it out to be.
1) It requires that you understand all of those basic sciences CONCEPTUALLY
2) It requires that you become proficient at reading challenging experimental passages and boiling them down to their basic components.
Ask yourself honestly, how good at those two items were you when you took the exam before? I'll bet that if I asked you right now to teach me the underlying CONCEPTS, the how and why, behind major topics like equilibrium, catalysis, central dogma, etc., you'd struggle to confidently do so. I'm being a bit presumptuous there, but I always start with my retake students by asking them a few basic questions about acid/base or equilibrium, something like "Tell me, what is Keq?" or "Describe and draw out for me what is going on with all of the molecules in the solution during every step of a titration." I usually get blank stares or pretty messy attempts. It is surprising how often we've only memorized some random stuff and when someone asks us to teach it back to someone else, or explain how it works at its most basic level, we can't. So, that's actually good news. Once you can confidently conceptualize and reteach all of the major topics on the AAMC list, and once you no longer feel intimidated by hairy experimental passages, then you can absolutely sit for the exam again and expect NOT to earn a score anywhere near your previous one.
I sensed in your original post a sense of helplessness, almost "What can I do now?" My two points above are an effort to show you that there is a lot you can still do. Once you've changed your behavior and conceptual understanding significantly, I promise you the score will follow.
]
