So, I would take it one step at a time. You have good GCSEs in the bank, keep the faith, get established a study (and relaxation) routine and see where you get to. You can only do your best, you may get to medicine grades, if you don’t you can do something else rewarding or resit. I lost momentum with similar reservations to yourself and failed my A levels. In hindsight it was a mistake, that I had to pick up the pieces from later. Uni and a science degree is a great experience and sets you up for a good career