This is just a thought based on my own experiences, but have you considered trying a totally different learning mechanism?
For instance, I'm absolutely godawful at math. I dont think I ever reached a third-grade level, really. I could do addition and subtraction, so long as the numbers arent too big. I could very, very, very slowly do multiplication, but there will be many errors. I had no idea how to do division. None. And anything beyond that is not even worth trying, I definitely couldnt do it.
Back in school, math classes were always failing grades, really. I was never a good student, but that was the worst of all the different classes.
But all of that was seriously the wrong way for me to learn anything. Just sitting there listening to brain-meltingly boring lectures being given by a teacher who likely didnt even want to be there? Yeah, that works for some, doesnt work for me.
Recently I just sort of abruptly decided "I'm gonna try the math again, but let's try it differently this time". Note that it's been well over a decade since I got out of college (and I wasnt any better there). I picked up a book, "All in One Basic Math and Pre-Algebra For Dummies" and the workbook that goes along with it (which is basically full of quizzes that are meant to be used with each chapter of the main book). I've had good results with the "for dummies" line of books before in various subjects (which includes computer stuff, an area where I absolutely do know what I'm doing, but there's always more to learn). So it's like, hey, let's give it a try.
And ya know what, I found myself successfully doing long division for the first time since... er... since ever, really. I never grasped that back in school. But I realize now, that was seriously because of the teaching method. Lectures and classes just dont work for everyone. Using a method that is compatible for you though, can change everything and show that hey, maybe this subject here (whatever it is) isnt impossible after all, with an approach that actually freaking works. And one that actually respects your time and any challenges you might have (like how I *must* get up and pace around every now and then, I couldnt do that in class). I still have a very long way to go, mind you. I'm not exactly at algebra yet (or even close). But I know now that I *can* get there, so long as I persist with it.
There are other ways of learning too, many ways, just takes some exploring and experimenting to find them.
What I'm saying is: just because something aint clicking, that doesnt immediately mean that you're stupid... instead, it might mean you need a different toolset for learning. Though of course the stupid education system tends to present the idea of classes and lectures and such as the only way to learn... but that's a whole other irritating discussion.
I do want to also second what
@Aspychata said though: everyone's good at different things. How about trying something completely new?