You are beginning to realise and accept that it is over. That underlying hope of getting back together is getting crushed as time goes by and that's why you feel the pain. The fear that she might have moved on is there because if she has then all this is definitely real and permanent. Don't fall into the trap of trying to analyse what the fact she might have moved on that fast says about your relationship. Believe me I have gone down that path and it won't lead anywhere. The truth is that she is no longer in a relationship and is free to move on as are you.
Just try and focus on your exams. I know its hard but you can do this