no such thing as silly mistakes. there is always a reason why you missed a question, even if that reason ends up being that the answer key was incorrect. "I misread the question" is not a silly mistake...it means you misread the question. Unfortunately, on multiple choice exams there is no appreciable difference between "misreading the question" and "I literally dont know a single thing about what this question is asking".
The most valuable thing I recommend that you probably dont do already is to always do postmortems on problem sets, quizzes, exams, all of it. Go question by question and review your logic. Why did you choose this answer, instead of this other one? If you changed your answer after finishing the exam then something about that question made you doubt yourself, something about the correct answer seemed off, and something about the answer you changed your response to attracted you. You will most likely notice a pattern in your thinking if you do this enough and that will give you an opportunity to improve on your weaknesses not just in a particular subject but as a test-taker in general. I also suggest having a higher burden of proof for second-pass/changed answers than first-pass picks. If the exam is MC, always be doing process of elimination. Never pick an answer merely because you think it is correct, but because you know why every other choice is definitely wrong as well.
Don't take any exam or grade personally. MC tests are very poor ways to measure intelligence or ability and even if they were those things shouldnt determine your self-worth. I know it's definitely much easier said than done especially when it feels like you cant be anything less than perfect to get into medical school. The truth you should learn to accept is that you aren't perfect, and don't need to be, but it is essential that you are always looking for ways to improve. There is no getting over it, I don't think. I was never as much of a perfectionist as my peers, but even then I vividly remember having a dream about the single question I missed on an ochem final after taking the exam. It was a really easy question, "how many stereoisomers does this molecule have?" and it was some big complicated antibiotic; literally the only thing you had to do was count chiral centers and do 2^n. In the dream, I saw the molecule and woke up in the middle of the night knowing I had miscounted chiral centers by 1. Got the test back and lo and behold there was the missing chiral center. Did it matter? No. Did it shatter my id, ego, etc? No. And yet it haunted me in my dreams anyway. Have to learn to live with it.
