My insecurities and anger issues. Life.

I am going through crisis situation. I am a student (preparing for govt jobs). I prepared for exams diligently for 2years but couldn't clear it. My only friend(almost 7years)- I mistreat her, even abusive (physically at times) Coz of my attitude she has also became like me. I am over-possessive, insecure and jealous kind of person. I don't allow her to talk to any guy friend. I am afraid she might hookup with someone and leave me. I have lot of trust issues. She is ready to sacrifice everything, even her needs and other things for me but nothing seems to give me satisfaction. I still am worried of being left alone. Other fights lead her to abuse me as well and threatening to leave me. I don't like this side of mine or hers. I don't want to lose this single-most important person. according to her, i am controlling her and this suffocates her. i want to change but my anger issues and my insecurities always gets in way. coz of all this, i have lost focus in studies and also in life.