For three days now I've been having the feeling I'm not getting enough oxygen ... I wake up with it and go to sleep with it it last all day and has caused me to have more panic attacks

I'm consitrating on my breathing so I know I'm taking in deep breaths not hyperventilating and I'm not weezy so why do I feel this way its scarrying me to death... I also have the feeling I have to constantly swollow ... Does this happen to anyone???