You are probably dealing with a lot of stress and that makes you feel like things are going bad and you're hopeless. A lot of times when people are pushed to the edge like that, they do feel that taking their own life is the best option. But it isn't. Breaking up with someone is a part of life and most of us go through it sometime in our lives. It shouldn't be something that determines whether our lives are worth living or not.
As to why in particular you feel this way, I don't know. Most people actually don't feel like that so I can't say why you feel like that.
I HIGHLY suggest that you go to a counselor/therapist and tell him or her about your problems. They are more likely to help you in an effective way and are more qualified to give you advice than I am. If you have already tried that, find a new counselor. Not all counselors can help everyone. So try to find one that is right for you. Also talk about this with your friends and family. Don't just seek help on the internet because we can't do very much to actually help you. People in your lives are there for you and can do much more to get you through this. So if you are having this problem, seek immediate help to either friends, family, or a professional near you.
