I can understand how emotionally disturbed you must be in the last few months wherein you have realised that you are surprised by your changed personality. Someone who is very confident and social has now become an emotional wreck.
I want you to ask yourself if this is true love because true love is always unconditional. It just flows without any preconditions and its foundation is absolute trust. It appears from what you are sharing that there may be a lack of both these components of love. Have you ever spoken to him about what you think of this relationship?
The more both of you talk about each other's expectation the better will be your position in the relationship. Also please understand that all abusive relationship thrive because of an emotional loop which is formed by both the doer and the receiver. You need to muster enough courage to break the vicious cycle otherwise later in life this is going to become severe and beyond your control.
You need to rediscover your natural confidence and tell yourself that you deserve much more than what you are going through. You have a bright future ahead of you after completing medicine so think positively and talk to him openly and tell him how you feel about the relationship. If he is willing to accept you the way you are then it is fine else you know what is best for you.
Good luck and always believe whatever happens is for the good!