I drink several sodas a day, however lately when i drink my usual soda i have severe pain in the middle of my upper abdomen. why is this happening ?

Cut down : It sounds like you need to cut down on your carbonated drink consumption . Our bodies change with time and perhaps is not reacting as it did in the past . Perhaps there is an underlying problem that is being exacerbated by the sodas you drink. See your doctor

Cut down and quit : the soda and see your doctor, The caffeine and acid in the soda may be aggravating an inflamed stomach lining so see your doctor and be checked .