Sulfamethoxazole and water weight

I started taking Sulfameth 3 days ago 2 times per day. I have the this for a total of 14 days and after reading, am nervous about what may come. I already experience dry mouth and extreme thirst. I have already gained about 4-5 pounds since starting it, but I expect its mostly water weight, since I can't stop drinking!! I feel slightly dizzy and sluggish. One slight symptom that is mostly an annoyance is the skin around my nostrals feels tight and cold- almost numb- although its smooth to touch. I'm aftraid it might continue to the rest of my face. Also, my digestion has been all messed up.