Another thing to bear in mind is that if you have a photographic memory you may be autistic. It's definitely a trait that autistic people have more than others.
It all comes down in my opinion to repetition. If the way you approach everything is through repetition then it's very natural for you to have a photographic memory if you think about it or at least the way that you tend to cement that line of thinking into your brain.
I can remember when I was growing up in my early teens how I could watch a football game and do like an action replay in my head. It was always there but it was only when I did my A levels did my memory become really accurate
When I'd remember things I wouldn't have any doubt in my mind whatsoever what the answer was. It was that accuracy that defined it. People would tell me their grades in different modules and I'd repeat the grades back to them precisely, a year after.
Sadly my memory is not quite what it used to be but that's another story. Ask yourself this question. Can you remember precisely what someone said to you on facebook 6 years ago? I think someone who has a photographic memory can and to do so they simply look at a picture of their message box from six years ago. The picture will be accurate.
Keep on studying. It does you a lot of good in my opinion. Never stop. One word of advice though. Get good regular sleep and don't booze too much.