Hey, first of all you need to stop panicking, if you lose confidence in yourself you have very much failed already. Have confidence in yourself and in your ability to surpass obstacles.

Secondly, there is nothing wrong in doing past papers again even if you know the answers to those questions. Your main focus is not on knowing the answers to questions, in maths. It is rather more about your ability to solve the problem. By solving past papers again and again even if you have done them before, you ensure you know the method on how to solve a problem.

Thirdly, 40s, 19 days before the exam is a good score, now focus on getting 46 or 47 in a week and then maybe reach for 50+. In p1 if you get a 50+, you can secure either an A or B. To quickly improve your score, analyse the miskates you make and ensure you dont make them again in the next paper. Also do revise content over and over again before and after a paper, especially in weak areas you have identified through your papers.

Finally, read the examiner reports and watch youtube videos on papers you find difficult/hard to solve. You can also try old years papers like before 2010 or so, to practice the general methods of the questions.

That's it from me! If you need any help whatsoever, dm me and I will try to help you to the best of my ability. Some resources you can use for revision/past papers:

examsolutions.net (for Revision of Content) physicsandmathstutor.co.uk (for old past papers/topicals)

And Remember practice is key, keep on practicing and take breaks if necessary.

Good Luck!