Hey, It's commendable that you have been able to overlook acting on natural instincts of body and focus on studies seriously. Not everyone of your age can achieve this. Natural instincts of body tend to put tremendous pressure on you to act. You have been able to control your emotions & instincts completely through rational thinking & will power when you are awake & conscious however while asleep you do not have this sort of control on unexpressed energy of instincts. Continue reasoning on your stand of not engaging in masturbation while awake, however see how exactly you can express this instincts in another way, may be by engaging in jogging, work out or playing a game of your choice. Through meditation you can convert or direct this energy into another channel which however is a possibility only when you aren't very restless. Do not be affected or feel defeated by continuation of masturbation as it is for a while till you are able to establish another channel of physical expression. Good Luck.

Hello ,its quite natural at your age ,don't feel guilty ,you must learn to let it go.Its your preplanned act . Sometimes erotic thoughts or dreams could trigger sexual arousal .Stop watching sexually stimulating videos , books etc... Completely involve in studies these thoughts gradually fade away .