Drinking diet pop probably isn't going to make you diabetic, but you could be having an allergic reaction or intolerance of the artificial sweeteners. Drinking a lot of pop isn't good for you, even if it is diet....I think this is rather stating the obvious here.

Stop drinking the pop and go in for an evaluation by a doctor. If you do have diabetes, it's important that you know and change your lifestyle accordingly asap. The back pain is most likely unrelated unless your liver and kidney and such are on the down run because of your pop addiction. You could also try getting a mechanical adjustment by a chiropractor after your visit to an MD.

Alright thanks