What can I do to prevent myself from having the depression type of dual diagnosis?

I'm the only one who knows that I'm not happy. I only cry when I'm all alone inside my room and everybody else is already sleeping. When I was eleven, I had my life planned out. I have this clear blueprint in my head of the things that I will do. I was very confident about the plan and I was consistent in following the instructions I've set for myself. Then problems came. It's like the world just didn't want me to go ahead and do what I want. It made other plans and I wasn't prepared for them. I didn't have a plan B. So I just went on with my life and did what I was asked to do. I didn't make me feel happy. I wasn't satisfied with myself. I never planned on being a nobody. Lately I've been relying on alcohol to carry some of my burden. It was helpful while I was drinking and wasting time away but everything comes back the next morning. What am I supposed to do? I'm tired of contemplating about whether I should take my life or not. I just want to be happy again but I don't know how.

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