Personality...character...i want 2 change it....?

You have a wonderful character and that is your nature. You want to 'toughen up' a little and I have to agree your friends are right. How about you start working on yourself to gain confidence? Since you are an excellent student already, try getting physically fit. Some weight training and a course in self defense. There are many 'self defense' styles and most teach mental discipline. When you feel more physically confident you will naturally stand up for yourself. It will be slow changing but this goal, to be physically able to stand up for yourself, will make you more confident.