Continue with triple scienceWatch
Generally I would advise drop to Trilogy (are you doing AQA?) and get a better grade, unless you know you want to do A level, in which case the potential lower GCSE grade is worth it for being better prepared for A level.
I would advise you to not even think about doing A level Sciences without being able to get a 7-7 easily in trilogy or a 7 in the science/s you want to study and at least a 6 in the others if doing separates. I'm a Science teacher, do feel free to ask me any questions.
That’s my success story to try and inspire you to keep at triple science but if it’s not for you, then by all means change to combined. Good luck!