Should I take a gap year?

The first year of sixth form I completely failed it and lost all motivation and so I ended up repeating Year 12 again, however my school made me change two of my subjects.
After I realised the subject I failed the most and got a U in (biology), is what I want to study in university I took the exams outside.

I put in so much work and revision, however my grades throughout class have not seemed to improve and I quite messed up my science exams and I just seem to be waiting for results day to confirm this. My chemistry teacher has told me there's been no improvements in any of my results except my work ethic and motivation. I'm so worried I won't get the module grades to even apply to university this year and I don't know whether I should just apply for a really low offer at a university or settle for a different course or take a gap year and then apply as a mature student.

I found exams this year either incredibly hard or otherwise really easy that I underestimated them and seemed to have made so many silly errors that I didn't realise until my paper was taken away.

It will have taken me currently 3 years to finish A levels.