I can't figure out how or why they happen,but the last few days,and even a short period of time last month,I was having frequent panic attacks. All of a sudden from out of nowhere, I'll have a panic attack where I am breathing heavily and can't stop. What's worse is I can't breathe out for minutes after the attack begins. I'm starting to wonder if there's a real problem I am having and what I can do to curtail this.