I feel like I've said this multiple times, but:
1) Most definitely. Medicine is a competitive field, and if you're applying for the MOST COMPETITIVE FIELD at the MOST COMPETITIVE UNI, you're not gonna have a great time competing against those who have more consistent and high academic track-record over someone who's changed just now.
However no matter, Oxford won't even consider you, but Cambridge may, they take a slightly more holistic view to GCSEs and just table it as the Candidate profile as a whole, so be prepared to have a significantly better AS Level results, A Level predictions, personal statement and STRONG UKCAT/BMAT scores to compensate.
2) Does it really matter?
All Medicine courses are run by the GMC, and regulated by them, you get no hospital placement preference if you intend on being a Doctor, you still get the title of MD and Medical Doctor at the end of it no matter where you go, which was the goal was it not? The only thing that may impact is if you intend on working outside the NHS after you do placements etc. But if you work in the NHS long enough you'll be as assimilated as any other.
3) Study elsewhere
Be more strategic with your choices, honestly. 'Medicine' =/= The top 10 on the League rankings, you only have 4 applications, use them wisely, use them strategically.
If you decide nope with the UK, try studying elsewhere in the EU, a lot of people go Bulgaria or Slovakia, or the Netherlands etc, you still become a Doctor and get to practice (idk how the EU laws would apply though).
Tl;dr Medicine is as open-ended as you choose it to be, don't make it more difficult for yourself.