I have the same problem as you. I have ended up taking 3 as levels (biology, maths and chemistry) instead of doing 4 and having to carry an extra one through to a2. I figured that I should concentrate on getting 3 A's this year, and spend the rest of the time volunteering and doing sport teams. Im planning to do an EPQ at the end of AS over the summer holiday. If you get a good grade then I think it is worth the same as an AS level, and many unis credit it and see it as important. You can do it on whatever you want, so you can make it relevant to medicine. Ask your teachers to see if EPQ is an option.