Thanks for your question and I hope I can help! Apart from the usual good sleep/good rest, good diet and exercise, looking after your emotional wellbeing and taking breaks from study, have you ever used any memory aids or had an assessment on your learning style?
I found out a bit about my learning style when I was at Uni as an undergrad. as someone within the psycholgy dept. was researching it and I thought I would put myself forward, to further their research and also find out something useful about myself. The results found that I was a ‘holistic imager’ (or at least I think that was the term!) which meant I learned best visually and when I could see the whole picture together.
So I applied this to my studies and devised ‘mind mapping’ ways of learning – using spider diagrams and I drew pictures of theories and theorists for each of my psych modules (I think I was learning about 7 or 8 different psych areas at that time). I did this by reading through core texts at least a month or so in advance and synthesising the information into summary notes followed by key points – key points that I could read through and try to commit to memory. The one page mind map of the module area simply acted as a prompt for the key information. I also used a ‘mnemonic’ approach (mnemonic is a funny word!) – a memory aid which helps you remember more info by recalling the first letter of each word and stringing those letters together to make a word. A simple example of a mnemonic would be to say ROY G. BIV invented the rainbow. And just like that you have a memory aid for all the colours and in the right order (Red, Orange, Yellow, Green, Blue, Indigo and Violet).
So on the day of my exams I would use these 7 or 8 A4 pages as my final study notes and look back at additional notes if I felt I needed to refresh on a certain area/topic.
Anyway, hope this helps. Different things work for different people and we all learn best when we are feeling happy and positive. It might be a idea to approach someone in your school/college who can support you further with this.