Struggling to do well in as physics

Hi I need some help and advice as I really don't know how to improve my grades in physics.
I currently got my physics class test back on waves and I've done terrible on it (got 18/40). It's annoying because I actually thought I've done average on it as well. Its not just this test though. Every single physics test I've done led me into D's and E's and it's honestly so demotivating. Last term I asked my teacher what I should do to improve my grades and they told me to do practice questions which I've been doing but I don't see any progress in my grades doing them.
In the most recent test I've done, I used practice questions,flashcards and my class notes to help go through theory and questions yet I still did horrible.I honestly don't know what happened, I could do practice fine with practice questions but when I do an actual paper I mess up so badly and I forget key info and using certain equations. I'm used to do bad in my other subjects but I changed my revision methods and I'm currently doing well on them.
However, when I try to use the same revision methods or something different for physics, I still do bad.I have summer mocks at the end of June and I honestly want to bump my grade to a B somehow, I just don't know how. Can anyone help me out and give some advice?
i'm going to try and work hard in improving my grades and I know I need to put the effort in to do so, I just want to know what I should to try to do, to seen any progress. I would love to hear from people who may have been in the same boat as me before and how they managed to change their grades.
Hope to hear from someone.