fear of noises and time bombs called teacher's scream

i (15m) go to an islamic all-boys school (the idea of being agnostic doesn't help at all), and i'm not the same as my classmates, we don't have similar interests, but it never mattered back in the first 8 years in school, yet for some reason this year i feel annoyed and great headaches by the unorganized talking mess and chaos every bad class you know has, until i realized something, that i didn't actually feel scared of those noises, i was always afraid of the noises i believe will happen \*next class\* or \*next day\*, how to reduce that fear? and not to feel so worried about something that hasn't happened yet