i failed a unit test in sixth form

so i'm in year 12 and my aim is to get into oxford for english. this week i took a unit test in class for a science subject and i'm pretty sure i failed pretty badly. not only did i run out of time to finish the entire paper (I missed like almost 2 pages worth of questions which has never happened before and I'm feeling incredibly mad at myself for) but the ones which I did finish I felt really unconfident in and a lot of them confused the hell outa me. it's not because of lack of revision - I do try really hard to revise for this subject but it's difficult sometimes because i'm not sure what to do with exam skills and stuff and the knowledge is often hazy. it doesn't help that my teacher is not supportive at all and I can barely talk to them because they intimidate me way too much. hell - they don't even reply to my teams messages.
so basically now i'm f***ing worried because of course i need my predicted grades to apply, and i really don't want this to pull my grades down. because i'm applying to oxford i need the grades really soon and i don't know if it'll be enough time to turn things around and improve, or even if i do, if my teacher will recognise it and give me a good grade. admittedly i haven't done my mocks yet but i'm worried that even if i do really well on the mock my grades for this subject all year (lingering between Bs and low As) will pull it down eventually.
i'm so sad because i wanna go to oxford and this test and possibly my future bad predicted grade will just ruin my application chances. going to oxford has been my dream which i've been working towards diligently since year 9. i got great gcse grades with all As and A*s and my other sixth form subjects are fine. am i right to be this worried because i really don't want this one subject to pull me down. i do try and i promise i will keep trying still but like i said i think i've definitely failed this test. how can i ever make it up for the subject.
is anyone else in a similar conundrum? or even if you're not, if you think you have any good advice please reply. ngl i haven't felt this desperate in a while and would really appreciate some help. thank you so much.