I'm sorry that so many people made fun of your question, because if it was asked in seriousness, I think it deserves a serious answer.
It could be a result of ki beginning to move and strengthen in your body. It seems that one of the first places ki goes when there is a sufficient surplus is the sex organs. I think this has to do with the survival of the species.
In yoga, there are seven vital points of spiritual energy that run along the medial centerline of the body. In yoga, these points are called chakras. In Chinese medicine it's one of the primary maridians. In martial arts, if one of these points is struck with suffient force, the person will die.
The yoga masters know that as they create and store ki through their practice, that the first place ki wants to go is the sex organs. I think this is called the Earth chakra, and it is considered to be very base for those who are engaged in spiritual training. They therefore train themselves to get their ki to gradually flow upward through the seven chakras until the ki is centered in the highest chakra in the middle of the forehead.
In tai chi chuan, similar principles are followed.
People who practice yoga say that aikidoists concnetrate too much of their ki on the hara, one of the lower chakras, and that such practice can hinder spiritual progress. (Please don't kill me, I'm only the messenger.