Maths

Well like many I'm just no good at maths I'm what you call maths 'illiterate' I'm incapable of keeping more than 3 single digits in my head at once i'v taken up many lessons and extra classes but to no avail and no teacher seems to understand and instead teachers the rests the class. But now Gcses have arrived and i'm totally f*cked because they have raised the grade boundaries so high even for a C i am unable to get a pass therefore will be forced to retake but i will also fail the next maths exam because of my bad maths. What can i do?
and for those thinking i am just a lazy teenager, think again i am a very studious individual who enjoys leaning but is terrible at maths

Extra notes:
Every maths teacher i'v had since primary school has given up on me and refuse to help (including serval privately hired ones).
I get decent grades in other classes such as computer science with an A