You need to look at your life and decide whether what you are feeling is panic attacks, anxiety, worry, stress, phobia or misguided paranoia.
Everyone - with or without realising it - experience some form of stress each day of their lives. It mostly goes unnoticed, since we all have our individual ways of dealing with it. A trip to the coffee machine, or getting some fresh air, or even hovering at someone else�s desk for a chat/bit of banter, is often our way of subconsciously dealing with undetected stress or the cliche "stress management". In fact, most people don�t realise it at all � as per your Q.
Even these mild or short bursts of stress can lead to a general reduction in our wellbeing, immune systems, and health/mental state. As said above, a lot of illnesses are attributed to prolonged stress and anxiety. When our stress levels get out of control, so do our bodily functions (biologically and chemically speaking).
Again, as said above, it affects each individual in different ways, as each individual responds and deals with it (psychologically or subconsciously, that is) in our own ways. Our bodies never lie, and even if you think you are not stressed, the signs are often there. This is why a healthy diet and exercise and lots of �down� time should be a prerequisite within your daily and weekly life. Many employers recognise this as a promotion of work/life balance. It is very real.
In my own personal experience, it lasted for about a year (circa 6 years ago now) and was due to intensive work pressures and a lot of imposed and self-inflicted unachievable targets/conditions. It caused no end of illnesses and problems (intestinal etc) which I still occasionally get recurring today. I gained a lot of weight (some lose it), my skin went to pot and my 12 year relationship suffered irrecoverably.
Stress is not all in the mind, but that is where it starts.