Why is it every time I drink ice nestea I get a burning sensation in my stomach?

Maybe an ulcer. Several problems could cause abdominal burning sensation but the most common would be stomach irritation (gastritis) or even stomach ulcers. To figure out the actual cause you may need upper endoscopy (egd) which is very effective at diagnosing ulcers and gastritis and is a quick 5 minute procedure done with light IV sedation.