This is a long response, but I hope what I've said here is helpful. I've kind of rambled on a bit here, but I hope at least some of what I say is helpful. That being said, I fully encourage you to go with your gut and take the A levels you like and enjoy rather than what people (including myself) have said in this thread.
Your A level combo isn't bad in any sense, but it does limit your options. You might be good at Spanish, but unless you are 100% certain that medicine or any allied healthcare profession is for you, I wouldn't recommend it (I say medicine specifically because the subjects you are doing is definitely geared more towards a career in it for which a degree at Oxbridge isn't really required. You can get an MBBS degree from anywhere and still you will be OK for getting a job). You really need to broaden your options as much as you can just to have a layer of insurance in case things don't work out for you.
I understand Maths at A level may look scary, but trust me, it's made out to seem far worse than it actually is. You will have to put in the work for any A level, and the fact is people simply don't put in the time and effort required for it and then complain that it's difficult.There are a wealth of resources available online and it can be super helpful to have Maths as it really does broaden your options a bit more.
I did Maths, Further Maths, Chemistry and Computer Science. Now, if you asked me what my least favourite and most difficult A level was this year, I would hands down say Chemistry. Why? Because I didn't put enough work into it and it became a lot of work for me and it was kinda difficult because it didn't link to what I wanted to do in any way so there was little motivation for it (I'm doing CS at uni) and it meant that I had to put in a graft as we approached A level exams. The way people avoid maths, I was avoiding Chemistry because I had to prepare for admissions tests, interviews, finish my EPQ and my NEA so I had my fair share of things to do and it meant that unfortunately Chemistry took a backseat. I didn't dedicate enough time for it and as a result, I kind of suffered with it until I started putting the work in for it.
If you ask me, take your current subjects and see how it goes. If you find that you are struggling with Spanish (which many people in my year did), swap it for another subject of your interest. We had lots of people in my year doing exactly this. There were maybe 25 people doing A level Spanish in my year, but at the end of it, we only had 3 people who stuck with it all the way through (of whom one of them was actually from Spain) so it's not easy. Many people quickly realise it's not for them. If you struggle at the start of the year, it's a sign to say you need to change because it NEVER gets easier from that point onwards. Now when I say struggle, it means you are struggling with the content, not with the tests. When you move to Year 12, initially EVERYONE struggles with the structure of the exams, because the mark scheme is more strict and there are very few repetitions of questions involved unlike GCSE so don't go off what your marks say. Go off how you are finding the lessons. Is it interesting for you? Are you able to understand what's going on? Is the right level of support offered? Is it a subject where if your teacher miraculously disappeared or just gave up on your class that you would be able to teach yourself? These are the sorts of questions you need to ask yourself when considering your options. I'm not sure about the depth of the resources available for Spanish, but I can say for sure that there is a lot of things available for Maths.
Additionally, if you're looking at Oxbridge for generally any course, maths is a pretty good option to have (particularly considering you're going down the STEM route).
Good luck! I'm sure you'll make the right decision for yourself!