Uncontrollable anger. I shouldn't.

I have this friend, who is really close to me, got so used to her now that when she is out with other people it bugs me off.. I start behaving angry and distant and say words to make her feel miserable cause she made me feel miserable... And this is not what just is natural human tendancy... It is much more than that... I start to.over think and I have this fear of being replaced very easily which leads to doubt and then the thought process of how can she be happy with anybody else than me... Am I not good enough... And then I will make her feel miserable I will say things I don't mean and at the end of it she will be crying.... I have no control.left on my anger... And my thought process.... My overthinking makes me so angry that I could hurt myself... I don't know how to calm myself down... I need help... My fear of being replaced and thrown out of somebody's life makes me do things I shouldn't ....