I was the same way with regular coke, 3 - 4 cans a day, easy. It was one of my greatest addictions for sure, I couldn't think without it. Unfortunately my method to stop is difficult, but I quit cold turkey. That was difficult and I failed twice along the way. But eventually I stuck it out. 2 after quitting, I had a coke and hated it (ohh thank god). It has been 2 years now and I don't even consider, to be honest, once I got over the coke mountain my diet became a lot easier to improve and I eat extremely well now.
It's one of the worst products out there, quit now and don't look back.
(I realize cold turkey is the way you don't want to hear, but ...)