I'm Addicted

Can someone PLEASE tell me how to kick my caffeine addiction out of the window? I try and try and try to hold back and steer clear of it every day... but I fail miserably. The only kind of caffeine that I really drink is in the form of Starbucks, but it's starting to take a toll on my debit card as well as my damn body! I remember when I used to drink cokes and such like crazy and then decided to quit and only drink water... I lost a good amount of weight and my body felt great! Where's my willpower? I went from a venti caramel macchiato to a tall today and my head is throbbing because it's just not the same. I 'had' to 'give in' and buy a Mt. Dew because of my headache from the lack of caffeine... I'm weak!

Any comments/opinions/suggestions would be VERY MUCH APPRECIATED!