While a number of medical schools only consider Maths and Further Maths as a single A-level, you're still doing way more than you need to anyway. You could do Biology, Chemistry, and Maths only and be a suitable candidate - Further Maths (or Physics, or an EPQ) probably wouldn't add much to this regardless, outside of your personal interests or if you change your direction.
Quality is more important than quantity in applying - anywhere, but particularly for medicine. I would suggest you consider dropping one or two subjects before even considering an EPQ. In any case, an EPQ is only useful if you're pursuing it to explore a specific area of interest that you have an idea for what to do in it. Taking one just to add another qualification to your application is, as above, meaningless. You are also less likely to enjoy it and more likely to get a bad grade in it if you do that.