AS Level

So I am currently an Yr 13 A-level student and I am studying Biology, Chemistry and History. For me Biology and History are fine and I fully understand it, Chemistry is the issue. I don’t understand it one bit. My teacher has warned me multiple times that if i don’t do well in these mocks, she will have to make me do AS-Level instead of A-level. Despite me revising and prioritising chemistry, I still don’t understand it. I have even gotten tutors, asked random influencers online to help, and of course asked my teacher for help after class. I think for now I would like to come up with a back up plan in case I dont do well in my mock.
What careers can I go into with an AS level (if possible anything in healthcare)? Or is there a way for me to convince my teacher to let me attempt the A-Level?

I think it's really unfair your teacher has told you you can't do A level if you mess up the mocks. I appreciate we don't know the context but if you haven't already and it were me I'd appeal this and go above your teacher to head of dept or sixth form. Get any parent/carer on side and ask for a meeting to really go over what can be done to support you. If you're struggling, what are the school doing to help? Have they given you self study, revision technique suggestions and materials? There are some really good websites and videos out there that can help, depending on your spec. Have the school offered you additional sessions, revision classes, mentoring? Do you have a schedule of going over everything each day after class by yourself? How about your tutor? Maybe if they don't help, try and find another one. Chemistry is super hard but with time, dedication and appropriate support from school, it'll hopefully get a bit easier.