Forgotten everything???

ive just attempted a maths booklet that my maths teacher had given us to do thats due tomorrow but when i was going through it i got stuck on the first question ... and when i flicked through the whole booklet i realised i had forgotten everything ive learnt. literally all those maths lessons for years ive forgotten everything. and its not that surprising because even in class the next day i wold forget what we did last lesson and even when we go over the same topic 2-3 lessons in a row ill still end up forgetting it... i dont know whats wrong with me i find maths so difficult and i keep forgetting everything ive learned. ive even went home and made notes and gone over some topics but still i have forgotten everything - and i just had a mental breakdown because exams are so close and i think i might fail in maths .. idk what to do please help .. why do i keep forgetting maths ? i was doing fine until year 10 when i started forgetting everything... i think it happens with some other subjects too like science.. nearly all subjects to be honest . i dont know why ? its just that maths is the subject that ive forgotten basically everything on .