Dear service user, Thanks for writing to Healthcaremagic. I can see your concern. Pressure on penis during sleep and discharge of semen is normal thing. Semen is being manufactured by genital organs continuously; it has to be expelled by some means. This situation is just akin to a glass of full water to which you add more water, with the logical result that it overflows. If one neither has sex nor masturbation for long time, semen gets expelled in the form of night emissions, which is normal. It does not point to any disease of sex organs. Sexual arousal can occur many times without our conscious awareness. This may happen during sleep too. This thing has no effect on penis size over a period of time. This is harmless and absolutely normal. No need to worry about. Wish you good health.