Hello, sorry to hear you've been stressing over GCSE Music.
I am also doing the Edexcel course and have some tips for revision.
When revising the set works, I recommend focusing on the 5 key features of each set work: Tonality, Texture, Structure, Instrumentation and Structure. Make notes on these and test yourself on them. Furthermore, I suggest you listen to all of the set works whilst following along in the anthology.
I hope I was able to help you.
Thanks,
arthur23