What am I doing wrong?

For reference, I'm doing Edexell Politics alongside English Lit and Maths.

Over the course of year 12 and 13, my grades in politics have gradually gone down and got a D in my most recent mock. Unfortunately, my teacher is rather unhelpful and doesn't give feedback/advice on essays, even after I approached him and asked him directly. This is particularly frustrating as I feel like I understand the content, learned plenty of examples and actively added evaluation and counter arguments into my essays. I'm not sure where I've gone wrong and how I need to improve.

I'm getting quite worried and overwhelmed as it's getting close to exams and I'm not sure what more to do. Are there any specific phrasings, structures etc that edexell like to see in essays? Just looking for advice as my teacher has not given any exam specific guidelines on what to include in essays, and I'm wondering if the exam technique is what I'm missing out on.