Hi Orange,
While the CACHE level 2 course is equivalent to a GCSE, it isn't a GCSE. A GCSE is a general certificate of secondary education, whereas a CACHE is the Council for Awards in Care, Health and Education. They're on equivalent levels in terms of complexity, but they're different qualifications.
I would say (it's a bit late now, but with A levels looming in coming years), you shouldn't pick subjects to study because you think you can do well in them. Yes, to study medicine you'll need to have the best of the best grades (or take an alternative route), but you'll find you'll do better studying courses that directly relate to your interests.
GCSE's are used purely as a measure of your consistency in education when you go on to further studies, so the courses you're taking won't necessarily impact your options. Plus, even though the CACHE course is designed more for home/child care, it does demonstrate a caring nature. Medical schools love it if you can show them that!
All in all, it isn't a GCSE, but don't worry about it. It still bolsters your application and gives you the 'care' side that is also beneficial. Good luck.