Chemistry revision CCea

Hi I'm really really bad at chemistry. No matter how much I revise I still do rubbish, I'm scared I'll do bad and fail double award. My teachers for 4th and 5th year were and are awful they don't explain it very well at all. My exam is at the end of may and I've only revised 5/19 chapters and I'm starting to get worried it took me two weeks to learn those chapters and I learnt half of geography in 3days. Are there any websites that have like summary pages on all the stuff you need to know and explain it simply? My textbook dosnt explain things very well.. Any tips