Pop addict

I am very addicted to drinking Pepsi when I don't get it when I feel like I need one I get headaches and very tired and moody if i don't get it. Anyone else have a pop or caffeine need otherwise they get the same way??? How do u think I could kick this bad habit because everyone in my family drinks pop or some kind of fizzy soda and always hands me a pop during family events ?? I would like to stop drinking the amount that I am I currently drink at least a liter to two liters a day if it is a bad week I usually have about 4-6 of these and I know it is too much for my body I need to stop or have a set amount I allow myself to have