OK, so I'm studying the aeneid for my a-levels and honestly, I've read it about 6 times, but I cannot remember the plot, any characters names themes... nothing! Any ideas how to remember it?

You read this six times and cannot remember anything about the book. How are you going to pass an exam? Can you remember that books one through six are about Aenaes' journey to Italy and that books seven through twelve are about the War in Italy? That should be easy to remember. As you read through each chapter, write things down that are critical. You just cannot read and expect to hold everything to memory. Make an outline of the book.

To help you with key points:
SparkNotes: The Aeneid
Vergil's Aeneid