I like to change it up. I use raw milk, an avocado and/or yogurt, frozen fruit, and sometimes melted coconut oil. I had also heard that adding grass-fed gelatin can super charge a smoothie..... I might try it sometime, ha. :)
I use sweet leaf liquid stevia most of the time. They even have awesome flavors such as English toffee, raspberry chocolate, et cetera. Sometimes I also like to use local raw honey.
I am currently breastfeeding, and intense work-outs do not decrease my milk supply. I do need to be certain that I am eating enough, because that does seem to cause issues. I agree with all the other comments. :)