If I yawn during meditation, am I not meditating properly?

Answer 1

I answered an inquiry earlier regarding the "yawn"...
Thought you might be interested?
(Or scroll down to the end, after the *s, for a Free 5 Day "Meditation Made Easy" E-mail Mini-Course link)

“A MUST READ” ANSWER:
A yawn (synonyms chasma, pandiculation, oscitation from the Latin verb oscitare, to open the mouth wide) is a reflex of deep inhalation and exhalation associated with tiredness, stress, over-work, lack of stimulation, or boredom. Pandiculation is the term for the act of stretching and yawning. Yawning is a powerful non-verbal message with several possible meanings, depending on the circumstances. Another speculated reason for yawning is nervousness and is also claimed to help increase the state of alertness of a person - paratroopers were noted yawning right before their first jump. The exact causes of yawning are still undetermined.
Some claim that yawning is not caused by lack of oxygen, for the reason that yawning allegedly reduces oxygen intake compared to normal respiration. However, both of these are as controversial as a debate over yawning can be.
A recent(2007) hypothesis by Andrew C. Gallup and Gordon Gallup of the University of Albany states that yawning may be a means to keep the brain cool. Mammalian brains operate best when they are cool. In an experiment, he showed several groups of people videos of other people yawning. When the subjects held heat packs up to their foreheads while viewing the videos, they yawned often. But when they held cold packs up to their foreheads or breathed through their noses (another means of brain cooling), they did not yawn at all.
Another theory is that yawning is similar to stretching. Stretching, like yawning, increases blood pressure and heart rate while also flexing many muscles and joints. It is also theorized that yawning helps redistribute surfactant, an oil-like substance which coats the lungs and aids breathing. Some have observed that if one tries to stifle or prevent a yawn by clenching one's jaws shut, the yawn is unsatisfying. As such, the stretching of jaw and face muscles seems to be necessary for a satisfactory yawn.
The yawn reflex is often described as contagious: if one person yawns, this will cause another person to "sympathetically" yawn. Observing another person's yawning face (especially his/her eyes), or even reading about or thinking about yawning, can cause a person to yawn. You could possibly be yawning from reading this section or looking at these pictures (not shown). However, only about 55% of people in a given audience will respond to such a stimulus; fewer if only the mouth is shown in a visual stimulus. The proximate cause for contagious yawning may lie with mirror neurons, i.e. neurons in the frontal cortex of certain vertebrates, which upon being exposed to a stimulus from conspecific (same species) and occasionally interspecific organisms, activates the same regions in the brain. Mirror neurons have been proposed as a driving force for imitation which lies at the root of much human learning, e.g. language acquisition. Yawning may be an offshoot of the same imitative impulse. A 2007 study found that children with autism spectrum disorders, unlike typical children, did not yawn after seeing videos of other people yawning; this supports the claim that contagious yawning is based on the capacity for empathy.
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Answer 2

No, your just sleepy. Maybe you should wait and meditate when your a little more alert. If it is just your mind trying to distract you, just acknowledge the that you have yawned and let it pass without fixing on it and return to your breathing, mantra, whatever.

Answer 3

Well, is it a oh-this-is-so-boring kind of yawn, or just an I'm-really-tired yawn? If it's the latter, you probably need to breath deeper. If it's the former, you may not be cut out for medetation. ;-)