Generally the standard advice is to not pre-study for med school. Generally it's good to make sure fitness, relationships, nutrition and finances are in good shape before looking at academic prep. That said:
U of Toronto biochem is really good. Expensive.
Khan Academy is good. Free.
Firecracker is a board prep program used by med students. Everyone who uses it at my school says "I wished I started earlier" including those who started during M1.
Best of luck to you.