Hello,
I don't see a problem with continuing to drink diet sodas, Crystal Light, or iced tea with sweetener as long as it is done in moderation and you still drink plenty of plain water. Having a diet soda now and then actually helps me in certain situations, such as when eating out at a restaurant, I sip on my diet soda to keep from eating the fatty mozzarella cheese sticks my husband always gets as an appetizer...
It also helps me in the movie theatre to order a big diet soda and sip on it to avoid the mega buttered popcorn.
I have never had any bad effects from diet drinks...although if you are the type who is all natural, buys only organic produce, etc. you may not want to have the artificial sweeteners in these drinks-that is a personal choice.
I don't have the urge to drink constantly like you do, except on days that I am really busy and have neglected drinking enough water throughout the day-then it tends to hit me right at bedtime how thirsty I am...wierd huh?
I hope your tests turn out alright, I know from it being in my family-and I was a gestational diabetic myself, that the urge to drink a lot is a symptom of diabetes, as well as the urge to eat sweets all of the time...but some of us have that without being diabetic-and that is why we are here!
Have a good day!
Aphil