The anti-soda crusade is not seeing the forest for the trees. I don't know why people dwell on how evil it supposedly is. If it's regular soda it's simply sugar. It's empty, useless calories, but a couple cans/day are only 300 calories. I have at the moment 1-2 cans of regular a day, not including my diet soda, and it doesn't affect me more than 150 from any other source. I'm thin and master of my weight.
Spend less time on soda and more time on overall calories if you want results.
Anyway, to lose 14 lbs in 4 weeks would be a deficit of 1750 calories/day, assuming your metabolic requirements remain the same, which they would not. That's 12 cans of pop/day, which I doubt the OP was doing. Something else is going on, but people ABSOLUTELY NEED to reaize that weight can fluctuate a lot and it's not just fat. I can wake up one morning at 172 and the next day at 175 if I eat a lot that day, but it's not that I gained three lbs of fat. I merely have a higher store of water and glycogen.
Quiting soda consumption is no magic bullet.