I did absolutely disastrously bad in school. After being held back two years and put forward after failing another year, I finally passed high school by one half point. I was diagnosed as retarded. (In that time, in my school, autism was unknown.) I would have considered it wonderful to have had your grades.
Later in life I finally figured it out. I found that I cannot be taught, but I can learn. I found that being taught is a social thing, involving another person. I am not a social person and anything social is an almost total distraction from anything I am trying to learn. I must admit that I am mystified how other autistics can do so well in school.
My childhood dream was to be an electronics design engineer. Those dreams, however, was quickly dashed. No such thing as a retarded engineer.
My interest, however, kept me studying electronics theory and getting assembly and repair jobs. Fast forward - as it turned out, without school, even without college, I worked my way to being a senior electronics design engineer.
So, I say, don’t worry. It may not be easy, but diligence and passionate self-study can get you where you want to be.