Ahh good news! Went to the Doc and luckily he knew what wa going on. It looks like I and most of you are most likely suffering from something called "Hyperventilation Syndrome". Most all of the symptoms everyone has been experiencing are pretty much this syndrome to a T. Here's a link to a comprehensive medical overview of this including treatment - yay! Do yourself a favour and read the entire thing you'll be glad you did.
http://emedicine.medscape.com/article/8072
77-overview
It turns out most of this is anxienty induced and stress is usually what induces it - though there can be physical factors as well.
"The explanation of hyperventilation syndrome lies partially in the mechanics of breathing. Normal tidal volumes range from 35-45% of vital capacity at rest. The elastic recoil of the chest wall resists hyperinflation of the lungs beyond that level, and inspiratory volumes beyond this level are perceived as effort or dyspnea. Patients with hyperventilation syndrome tend to breathe by using the upper thorax rather than the diaphragm, resulting in chronically overinflated lungs. When stress induces a need to take a deep breath, the deep breathing is perceived as dyspnea. The sensation of dyspnea creates anxiety, which encourages more deep breathing, and a vicious cycle is created."
So in layman terms, it creates a Co2 deficency and your blood ph goes way too alkaline. This sets off even more panic signals in the brain creating a loop where you feel like you can't draw a deep breath. Same thing with yawning, your brain is the problem here. Your body wants to yawn to adjust Co2 levels but can't because your brain is basically stuck in a loop for survival mode. It's also why you get that constant sighing. There's nothing actually wrong with your lungs or throat it's your mind screwing up how you're breathing. Most people can correct this simply through breathing excercises, though you may need meds (benzodiazepines) - my doc just prescribed me some Lorazepam and said it'll probably do the trick itself. Just a word of caution - as my doc told me - these should be used very sparingly as they can create a physical dependancy and should only be used for acute anxiety...like now...just to get back to normal than stop taking them ASAP. Non-addictive anti-anxiety, therapy, healthy diet and regular excercise (it always comes back to that doesn't it) maybe requried for the long term and are the preferred treatment.
More from the article....
"Most patients with hyperventilation syndrome tend to breathe using the upper thorax and have hyperinflated lungs throughout the respiratory cycle. Because the residual lung volume is high, the patient is unable to take a full tidal volume and experiences dyspnea. Physically compressing the upper thorax and having the patient exhale maximally decreases hyperinflation of the lungs. Instructing the patient to breathe abdominally, using the diaphragm more than the chest wall, often leads to improvement in subjective dyspnea and eventually corrects many of the associated symptoms."
and...
"Stress reduction therapy, beta-blockers, and breathing retraining all have proven effective in reducing the intensity and the frequency of episodes of hyperventilation. If the diagnosis of hyperventilation syndrome has been established, the patient should be referred to an appropriate therapist to implement these techniques over the long term."
So you may need to see a respirologist, GI and/or ear, nose and throat specialists too. So make sure to ask your physician if they're familier with HVS, if not get them to follow up on it or recommend someone who is you you're not stuck in the cycle of misdiagnosis and no relief. You can also provide your doctor with the above link seeing as it's a medical paper written by doctors who specialize in HVS.
....
"Most patients with hyperventilation syndrome tend to breathe using the upper thorax and have hyperinflated lungs throughout the respiratory cycle. Because the residual lung volume is high, the patient is unable to take a full tidal volume and experiences dyspnea. Physically compressing the upper thorax and having the patient exhale maximally decreases hyperinflation of the lungs. Instructing the patient to breathe abdominally, using the diaphragm more than the chest wall, often leads to improvement in subjective dyspnea and eventually corrects many of the associated symptoms.
Diaphragmatic breathing slows the respiratory rate, gives the patient a distracting maneuver to perform when attacks occur, and gives the patient a sense of self-control during the episode. This technique has been shown to be very effective in a high proportion of patients with hyperventilation syndrome."
I'm going to follow up here with another post on some breathing excercises you can do that should help eliminate this problem. Also you can google or youtube searches for "Diaphragmatic breathing".