I don't feel comfortable giving you reasons to die or to live. I don't know how you feel and what you are going through, and I don't know how you feel about your girlfriend. If she loves you she will be hurt if you CTB. This is such a personal choice, only you can decide for yourself. Can you talk to her about these feelings, or do you think she couldn't understand you at all?
As you know, if you are successful you can only make this choice once, so if I were you I would spend a good time thinking about your feelings and what other options you have.