It's a central nervous system issue causing a state of almost contest anxiety. It's not "all in your head", it's all in your chemicals, something you don't really have much control over. The first step you need to do is quit all the bad talk about yourself. Never call yourself a "loser" again unless you're being ironic. Sincerely insulting yourself is a fantastic way to kill your confidence and make you more anxious. Youre a human being. I'm glad you've just accepted your stutter. Now start viewing yourself in a better light