Why do I struggle at maths so much?

Whenever I’m doing maths, despite how much progress I make, despite how much revision I do, despite how hard I try; I can never truly grasp maths, it’s so bad I struggle at basic mental addition. I feel abnormal, I watch as people excel through papers, whilst I can barely get over 50 in foundation. I’m genuinely getting worried as I feel as if I’m not going to pass maths even though I do try my best and do extra