Hi bedshaped2000
I think the main thing is, everything in moderation. If you're weaning yourself off the soft drinks, great. I can't see artificial sweetener in your coffee being a problem, assuming you don't drink 10 cups a day ;-) I was on Atkins a few years ago for ten weeks, and I subbed milk for cream because you're not allowed milk (due to the lactose) on Atkins. That said, you're allowed as many calories as you want on Atkins, so the cream being very high in calories didn't matter - it may for you.
What's to say there's not a problem with too much <insert another sweetener name here>? You may also find that much coke-type drink is also overloading you on caffeine, especially combined with coffee too. Generally, too much of anything isn't good for you.
You don't mention how much you actually drink in a day, so the peeing may simply be a result of large quantities of liquids in general.
Ali