If possible, might be good to talk to your personal tutor or other university support services/lecturers.
If you still enjoy medicine you could try and get support with learning. Personal Tutor could possibly advise on how /if possible to swap courses, if you wanted to do so.
You could also have a look into the courses you're considering swapping into (and others). i.e I've heard some people say there's more physics than chemistry in Chemical engineering (despite the name!), but that might not actually be the case.
Maybe worth looking into material science/engineering too - think that's also a course at sheffield.
Best of luck with whatever you decide to do,
and hope your situation clears up and things go well! 😄