Always Taking Deep Breaths...Answers??

Hello, I am a 23 year old male, for a few months I have been experiencing this weird sensation of always having to take a deep breath, its like I do it most of the day almost every day, I dont/havent had a cough or pain or any real respritory (sp?) symptoms, I have had palpitations (kinda fluttering in my chest) but not very often at all, not every day, not every week or 2 weeks. But I am ALWAYS worrying about my health, thinking about it, testing myself to see if I am breathing ok or what not. And that may be the root of it, I dont know, its almost like its a "habit". I feel pretty good, I dont feel sick or anything like that, but this problem makes me think that I am, you know? I was diagnosed with Panic Disorder when I was a Jr. in high school (so about 5-6 years ago) the Dr gave me meds and it all cleared up and went away. I dont get out much, and I dont excercise that often anymore, kind of out of shape. Never have had a history or heart problems or lung problems. In Sep. 09 my family had a pretty big tragedy and I had to move back home to help with everything, I tell myself there is no way that could be the cause of all this, but maybe?? I really dont know. Anyway Ill leave it at that for now, If ANYONE has any advice or has had this kind of experience please get at me, it would GREATLY help. Much Thx. :-D