I rely on my girlfriend for my happiness
Why do you depend on her for your happiness?
My personality id weak, dull and irritating without her around.
She seems really important to you, but it's imperative that you learn to love yourself so that you can become an independent, confident, and responsible person who she would like to be around. You are worthy, just as much as anyone else.
Without her, I would just be fine not exisiting.
I understand that you seem to really love her, but it feels very one-sided and one day if she ends up breaking up with you, then you may do something drastic like taking your own life. I do not suggest you go down that path, so I suggest you meet friends and get contact with your family members, so that you will have a health balance of happiness and not just with one person.