Yawning, how i hate you.

Im trying to get to sleep and trying to do some techniques to help me get my first LD. Im sititng there and all is good and im about 3/4 to a sleep then a yawn comes. now i know im fully awake. The worst part is that i can't stop yawning. I yawn probally 15 times in a half hour. Im starting to think this is more of a physcological problem because im thinking about not yawning and therefor i yawn. Anybody have tips to help me to stop yawning?