How to Avoid Failing at Basic Arithmetic

hi! i'm in calc bc. i got a 5 on the calc ab exam and my grade last year always remained a high A. however, for some reason this year i cannot seem to stop making dumb mistakes. i understand the material and the calculus, but i'll forget to write a negative or say two negatives multipled is a negative. i also keep miswriting my own work at some points. i don't know what to do because on my last test i ended up getting a low C on it because of these careless errors. i have another test this week and i'm studying a ton but i still keep making these erros. any advice?