I have been a Coca-Cola addicted for years, I was drinking at least a liter per day, sometimes two, this when I was a teenager. I've never been fat nor with health problem. One day I decided to stop, It took me two weeks of headaches to kick it off, but now I'm far less nervous, I sleep much better and my life improved a lot. Still if I drink a can of coke I'll have headaches for at least two days, as I don't drink any caffeine.

So do it, use painkillers when you can't handle the pain, but don't exaggerate with them, it's worth it not only for the long run but you will quickly see improvements on your daily life, good luck!