Your GCSEs do not rule you out from being able to apply for medicine. It's very true that medicine attracts many applicants with a high number of A*s and you will be in competition with them, but there is far more to a medicine application than just GCSEs, and even then, there's far more to an application than just academics. Academically, if you do well in your A levels, then you're in with a shot!
I echo the points of the above, graduate entry medicine is very competitive. I'd say go for medicine now if it's what you want to do, bud.