The struggle is real, I'm doing triple science so I have to revise core, additional and triple! I revise by making a timetable, but instead of using times, I use pages of my cgp revision guides. For example, I made a timetable before my mocks to do 7 pages of Biology and 7 pages of Chemistry one day, and do 7 pages of Physics and 7 pages of Chemistry the next, etc. Obviously, we've got 5 months so if you do 2 pages or 4 pages a day, I think you'd have time to go over core and additional science more than twice. I've also printed off the specs for my exam board and i highlight all the content that I know I can do confidently. I'm hoping to finish all of it by May. I personally like to revise by making notes in different colours and using different highlighters and then saying key points out loud without looking at my guide or notes to see if I have everything covered. Good Luck!