This may seem counterintuitive, but move the mic closer and turn the gain way down. Then start speaking louder. The AT2020 is a mic designed for vocal broadcasting and it's used in studios and radio stations all over the place. If it's picking up your breath from 18 inches away, the input volume is too high. Turn that s**t down, kick your voice up a notch and you'll be fine. It's all about learning how to work the mic and that mic is best 6-8 inches from your mouth and 45 degrees to either side.
Also, the pop filter suggestion made me laugh out loud and now people nearby are looking at me funny. It's not a breath filter or a noise filter. It's a pop filter and has a very particular purpose.