My girl comes online, and if she doesnt reply soon, I get angry and throw tantrums on her. This is hurting our relationship. How do I control my temper?

Seek counseling. Your reaction shows both insecurity and a desire to control. Why you have this set of feelings is beyond an answer at this site.You need to seek out a non-related counselor to explore what has happened in your life to trigger such feelings. If you don't, it will get worse and you will drive people away from you.