Going to fail maths GCSE

I do the Edexcel exam board and am down for higher
So for the whole of year 10 apart from one term I did not have a teacher in any of my subjects, I managed to fix my grades with all my subjects obviously not to the standards they were 8/9s but now I get 5/6/7s. Apart from in maths so in my year 10 summer mock I got a 4 and this year in my November mocks I also got a 4. Before this I was getting 5s as maths has never been my best but now I am barely scrapping by a 4, I need help I'm so scared that I'm going to fail maths. I want to start revising it but I don't want to have to sacrifice my other decent grades for maths. I really need some help, and any for double/combined science will be helpful. I do not have a maths teacher so I have no clue where to start and not that long till exams thanks

I'm a little curious as why you don't have a maths teacher.

Have you googled for videos on how to improve your GCSE grades? See the following (found on the first page of Google, so there are more) for example:

Maths:
https://www.youtube.com/watch?v=aJEkjuN9qJ4
https://www.youtube.com/watch?v=f4Pa9hYX7rg
https://www.youtube.com/watch?v=PBRrL8Bhdlg
https://www.youtube.com/watch?v=5RwbT5D6sh8
https://www.youtube.com/watch?v=y8yC4bBYyos
https://www.youtube.com/watch?v=Wb8ZyXl_nps
https://www.youtube.com/watch?v=rC5TSw744lk

Science:
https://www.youtube.com/watch?v=NL7u7vZ4mnM
https://www.youtube.com/watch?v=F_9F_kkp37g
https://www.youtube.com/watch?v=mWX900ZrwwU
https://www.youtube.com/watch?v=YIIRwEIUBzo

Most of the above calls for you to do a lot of past papers, review your answers, and then do the questions you got wrong again until you get full marks before moving onto the next paper.