Re: sperm not come out what happen when mastrbating
You could have retrograde ejaculation, where the little flapper value that routes semen out of the penis sends it instead up to the kidneys. If this is happening, you may have a cloudy urine due to the semen. Holding the penis too tight can also prevent the semen from coming out and causing it to back up. That probably won't do any harm if done occasionally but, in general, don't clamp down on the penis too much, as it will make it more difficult to reach orgams with a woman, as you will be so used to the tight pressure that her much weaker vaginal muscles will not be able to match.