Suggestion for low carb good quality protein powder

I have a sweet tooth so just looking for a low carb and low fat alternative to sweet treats. I am unsure as to which protein to get that will cover all of the mentioned above. I am also unsure if I should get whey or soy protein as in, which is better in terms of carb count. Lastly, as I am student I am looking for something GOOD QUALITY but also a little lighter on the pocket.