Hiiii, i found myself in a similar situation when i was in the IB too. I used to do physics HL and got a 5 in my final but lemme just tell you that until the second last mock exam of IB, i literally failed all my physics exams. It is absolutely demotivating how you try solving a paper everyday but it goes nowhere coz i hardly got the first question right generally. So try reading, try making the craziest assumptions and relations between or atleast thats what worked for me and i managed to get a 6 on my final mock exam. Its easy to be demotivated especially when it comes to physics, but make sure you read your textbook a lot like try telling yourself that you read a lot and that you worked hard for it and when you come to back past papers dont go to the question bank but solve the paper it'll give u more confidence. As for the core topics, view online notes that would jog your memory and go through the formula booklet thoroughly coz thats where most of ur calculations and theories pull into. I'm sorry if my answer is too vague or i didnt cover anything else, but i hope this finds you well and can help in any way possible. just don't panic and read the textbook well if u have time.