If you struggle with Maths then... don't do it. Do whatever subject is most likely to result in you getting the highest A Level grade, simple as that.
The idea that Maths is required for Medicine is purest bull****, perpetrated by people who think that because Maths is needed for some sciences and Medicine has science in it, that means something. It does not!
Just do a well-respected A Level and aim for good grades. Taking a subject where you're going to struggle to get a good grade is frankly shooting yourself in the foot on poor advice.