Hi,
You have come of age man! What almost every man experience is what you experienced. A night fall or nocturnal emission, also known as sleep ejaculation. It's involuntary act of nature, that starts sometime during teenage and occurs most commonly until young adulthood. It sometimes occurs during sex dreams, but sometimes without any dreams too. And it is associated with full bladder.. that is, the chances of night emissions are more when your bladder is full during sleep. It occurs in men who masturbate as well as those who dont. Young women also experience a similar phenomenon, but we dont call them sleep emissions, instead we call them sleep orgasms.
They are more frequent in men who think, read, see mucuh sex and less in those who are otherwise preoccupied (studies, job etc.).
Sleep emissions are natural! They are perhaps the body's way of testing your ejaculatory mechanisms; perhaps also a way to clear up old stock of semen paving way for production of new stock and also to test-run the on-off controls of sperm and semen production.
So let the body do its job. You dont have to be alarmed about this, as night falls cause NO harm to your health or future sexual life. Be assured that they dont cause premature ejaculation or erectile dysfunction too.
Next Steps
All you have to do is 1) stop worrying about this 2) Just laugh off when they occur, wash yourself and mind your business 3) stop purposely watching / reading porn / thinking much about sex etc. 4) Remember it is yuor birth-right to experience nocturnal emissions (I mean they are so common, but I must clarify that there are rare men who never experienced nocturnal emissions at all, but that is okay too).