I'm addicted to caffeine. I drink 5 or 6 extra-large coffees a day and have a few glasses of Diet Coke every evening. If I sleep late on the weekend, I wake up with a wicked headache from caffeine withdrawal.
I had to give up caffeine a few years ago when I was going through a very bad bout of IBS. I went on a diet that prohibited caffeine. I spent a weekend tapering my caffeine consumption... replacing coffee with peppermint tea or decaf coffee. I had to take Ibuprofen for the headaches, but within a week I was off caffeine completely and no longer had headaches. If you can find a caffeine-free herbal tea that you really like, it can give you that same comforting feeling of having a cup of coffee. I also started drinking a lot more water... adding a slice of lime made it feel more "special." Mixing 1/2 cranberry juice with 1/2 club soda was another favourite drink during that time. My GI tract thanked me for it.
Here's something else I noticed... I was so addicted to caffeine that once I cut it out of my life, I found out that it hadn't really been perking me up like I thought it was. When you build up such a high tolerance it has very little stimulant effect, so I didn't find that I was any more tired or less energetic without it. I actually had more energy because I didn't feel so sick to my stomach all the time.
I wish I had stayed off the caffeine. I know it's bad for my tummy and increases my anxiety. I need to quit... again... I also need to quit smoking... again.
Good luck with quitting. I actually found it much less difficult to give up caffeine than I thought I would. It was basically a psychological addiction. I just had to find another hot drink that I enjoyed and peppermint or ginger tea (I like the zing!) did the trick for me.