Yup I've had it happen. I've heard that it's a result of getting turned on. The vagina length's sortof when you get really turned on and as a result sometimes sucks air in.
As far as I know there's not a lot you can do about it. Just have a good laugh and tell your hunny that at least it tells him that you are REALLY turned on by him.
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"Always learn the rules so that you can break them properly." Dalai Lama
My Karma just ran over your Dogma.