Hi Arif Night fall or swapnadosh( as it is known as ) is not a dosh at all. When a boy grows into adulthood, the body has various changes like increased height, increased in size of genital organs, raised level of testosterone, increased interest in opposite sex, desire to have sex and deepening of voice . your body starts producing seminal fluid . It works like your lacrymal gland- when you feel sad ,tears will flow down your cheeks or your salivary glands- when you smell good food, you will have salivary secretions- whether you like it or not. This is not under your control and you are never going to be short of saliva or tears, despite whatever quantity you secrete. Similarly, seminal vesicles and prostate secrete seminal fluid under the influence of hormone Testosterone and it is not under your control . your body secrets the maximum amount of testosterone in early morning and in addition, the sleep pattern during late hours of night are such that it has maximum dreams so testosterone secretion during this time produce erotic response in body and penile erection ( you are unaware of this)- thus causing seminal discharge. It is a perfectly normal sexual developmental phase . Problem arises only when someone gets anxiety and guilt so just enjoy this feeling as well just like normal sex Erect penis size of 5 inches is with in normal range so no worries Best Wishes