There are breathing exercises that can help with this. Anxious people tend to breathe shallowly, from their upper chests. Relaxed breathing is from deep in the abdomen. You can learn this by seeing a therapist expert in treating anxiety problems or you can learn it from a yoga teacher or spiritual teacher of Buddhist and Hindu breathing techniques.
So you can not breath easily? You have some breathing problem? Have you visited a doctor?
It's the breathing that makes me feel like fainting. Sorry I wasn't clear.
What do you mean, have to concentrate on your breathing? Is it the breathing that's making you feel faint? Not clear.