If you were breathing well, you wouldn't be feeling like you're passing out? You can also be unconsciously holding your breath so not breathing well in that sense. Have you ever fainted before? I almost did once in church when I was about 10 (stood up too soon or fast or long or something to sing a hymn) and first all the color went from my vision and then it got to be tunnel vision. It was especially frightening and confusing for me because I'd never had anything like it. I had to "infer" with my bright 10 year old self that maybe I was going to faint because it had never happened to me before. Could be, since you're "new to this whole anxiety thing" that some of your symptoms are adding to your anxiety, adding to the whole effect.