I just want to be prepared in case someone tries to take advantage of me.
Might I suggest Tae Kwon Do lessons. No, I am serious. I don't mean that you should beat hell out of people, though it's definitely a good ability to have if need be. No. If you get a good quality teacher, the martial arts training can instill in you self discipline, self respect and self confidence. Many fine qualities that help you stand up in life and assert yourself in positive ways.
Absolutely. Couldn't agree with you more. Any Martial Art would be really beneficial in building self confidence and self esteem.