I pretty much replaced sugared carbonated drinks with diet carbonated drinks.

Honestly, that's not much of a trade-off. While the diet soda means you aren't consuming any calories, that doesn't mean you won't gain weight by drinking them. The artificial sweeteners (aspartame, saccharin, and sucralose) have the same impact on the body as sugar does; they trigger insulin, which sends the body into fat storage mode, thus leading to weight gain.

There was a study done, in Minnesota or Wisconsin or some other state where they speak weird, which showed that by simply drinking one diet soda a day, people were almost 40% more likely to develop diabetes, high blood pressure, elevated glucose levels, raised cholesterol, and put the drinkers at high risk for heart disease and stroke.

Another non-benefit is that diet sodas still have citric acid in them, which is what erodes the enamel of our teeth. There was a study released in the General Dentistry journal which compared the teeth of a cocaine addict, a meth addict, and a soda addict. The study found the same levels of erosion between the three individuals.

Now, all of that said, I'm no doctor (but I stayed at a Holiday Inn last night!). When I discovered most of what I just outlined above, some three years ago, I was drinking in excess of 15-20 cans of leaded (non-diet) Dr. Pepper each and every day, and considering switching to unleaded (diet) to be "healthier". When I learned that it wasn't any healthier, and might actually be more harmful, I just up and quit Dr. Pepper altogether and instead switched to water. Honestly, I haven't noticed any advantages health-wise, but the relief my wallet felt was immediate and amazing.

TL;DR: Diet or not, that shit is still bad for you. If you can't do plain or flavored water, try sparkling water.