I think you know the answer here and taking your own life is not it.

You are young and as much as you don't want to or believe this, there will be others that you will feel like this about, trust me.

However there is a lesson here you must learn. The charlie has got to go NOW, end of. Your drinking must also be got under control, make sure you limit yourself and stick to it. Then, in a few months, when you are clean and sober go and apologise to your old girlfriend, not for reconciliation but for closure and to recognise her efforts, she will appreciate it.

Then go an enjoy your life and take this as a life experience.