Welcome Kalie!
First off you are not alone! Feeling like your "not here", being worried you'll stop breathing and a fear your going to die are common with anxiety. I'm speaking from personal experience. As Scaredy Cat mentioned, CBT therapy along with medication has helped a lot of people. I currently see a therapist once a week & it has helped me quite a bit!
Learning how to cope & not dwell on a certain fear as well as accepting the symptoms as a sign of anxiety is very important but takes lots of practice. I'm still learning most definitely but I turn to here & therapy and it gets me thru. Best of luck, keep posting