Grammar question

Just fielding a question. My whole life I have not been able to learn proper grammar rules, even as a child. English is my first and only language. I was and am very fussy with proper spelling of words by way of a dictionary in early grade school and Google now (I am almost 65 ) and read well but I am wondering why I could never learn grammar rules, it just seemed incomprehensible to me. I have tried those quizzes on social media once in a while to test my English knowledge, usually they have results advising that I most likely passed grade 2 but not to give up. I am tending to blame my issue on a type of learning disability ( there are other issues I have where certain concepts are beyond me and out of my grasp although they should not be). Any opinions?