Are you in Year 12 or Year 13 at the moment?
If you're in Year 12, I would recommend keeping the English Literature during this year so that you can develop some skills for essay writing and analytical thinking, but you can always drop it at the beginning of Year 13. You can always see how your Year 12 exams go and work it out from there. If it gets too much during the year, you can drop it then, but I'd say stick with it and get used to a high workload, as it will increase in Year 13 even studying only 3.
If you're in Year 13, there is no reason to keep it unless you really enjoy it and it won't affect your other subjects too much. Since you want to study medicine, you will need to focus on the other subjects, so I'd drop it.