You may not think you're stressed, you enjoy your job, you go out enough, you have a life. But working for a long time at the computer can make you stressed, keeping a bad posture while you're doing it will make it worse.
When our minds are stressed, we breathe shorter, shallower breaths, not deep enough to exhale all of the CO2 out of our bodies. We want to take a deep breath because it's the body's natural mechanism for rotating the air in our lungs. Breathing short breaths is like what you would automatically do when the air you're breathing is of bad quality, such as if you were in a burning down house. Maintaining this bad breathing leads to not enough good oxygen getting to the lungs, which can then cause air-hunger (gasping for breath, insatiable need for a deep breath), nervousness, tremors, tight chest, palpitations, panic attacks, feelings of terror, dizzyness etc.
Things that can help ease symptoms-
Less hours at the pc, take regular, strict breaks, check your posture every 1/2 hour, if you don't know what correct posture is for computer use, find out. Make sure the lighting in the room is good, the air and air temperature is good. Don't ignore those things.
Take exercise, eat regularly (not eating regularly can make the body stressed), find something you can do if you start to feel strange (I peel fruit, sounds weird but it concentrates your mind on one thing and your body sets the breathing right. In yoga they teach you to focus on the ticking of a clock, whatever works. It's a form of meditation.
Try to breathe through your nose at all times, even when you feel panicky. Normal breathing is about 9 times per minute, check yourself every now and then.
Learn pranayama, forget Buteyko- it's a pointless cashcow, you won't find anything out for free, and what you do find out can be learnt through Yoga, which has been practiced for thousands of years, who are you going to trust?
Get at least 7 hours sleep a night, learn to notice when your mind is tired (you might slouch, you might feel strange between the eyes, you might frown etc)
Stop taking 1/2 of the medication you've been given, just to test yourself. . . reasons follow.
I've had it all, pulmonary tests, cardio tests, blood tests, ER trips. I was diagnosed with asthma, then told I didn't have it, then told I had hyperthyroidism, then told I didn't, then brachycardia, then anaphylaxis. . .the list goes on.
I found that some of the medicine given to me (inparticular bronchodilators) induced unpleasant interactions in me with things like coffee or alcohol, the unpleasant interactions would then give me another symptom (like pins and needles in my arms and legs) which would then make me worry more, the doctors would give me one more medicine to add to my carrier bag, and the problems kept getting worse.
Stopping taking the asthma meds helped me 50%, stopping the rest helped another 30%. Finally I'm back at square one over a year and a half away before I started taking anything and I just had a problem catching a deep breath.
I have to say that my problems really started when I gave up smoking. It puts a huge stress on your body, one that you can't imagine, it infects your senses, your brain, your dreams, and your fight/flight response can be seriously mal-aligned.
Avoid stress at all costs, learn ways to calm down. Even if you don't believe it, try to learn why people meditate and find out your own way of doing it, it really helps.
Change your diet, eat regular meals, don't eat too much fat, over-eating can have negative affects on your breathing. Also make sure your clothes aren't too tight, if they are it promotes bad breathing (breathing up through the top part of your lungs) practice breathing out through the very bottom of your stomach (diaphragm breathing) you get more air into your lungs and it's much more natural.
Doctors are useless, you have to find this out by yourself.
Good luck & stay healthy.