Nocturnal pollutions are caused by lust. If one is not aware of where, how, and why lust is acting in the physical plane, this indicates one is asleep and that more comprehension is needed.
Comprehension first begins by seeing where lust manifests, how, and why, what its nutrition (impressions) is, what thoughts, feelings, and impulses constitute the defect, etc.
Meditation deepens when we have first seen such lustful egos in action and are working to comprehend such errors based on direct observation. If we do not see where such egos come from or how they manifest in daily life, it means we need to strengthen our vigilance and self-observation.
Do not believe that lust is gone because you don't see it! That is a sophism of distraction. Instead, intensify your observation and you will catch that unmistakable flavor of temptation when it arrives in your three brains, in response to ordeals in the physical plane (which will then transfer over into the astral plane).
The more restraint we show in our physical body through self-observation and comprehension, such self-restraint will then transfer over into the dream state when one is more vulnerable.
If you have a pollution, transmute your energies and meditate on the dream, what you remember, what caused the fall, etc. This takes tremendous super-efforts, but is essential if one suffers a fall.
Nocturnal pollutions end when the egos of pollutions are comprehended and annihilated.
"With patience possess ye your souls."
For thirty years I sought God. But when I looked carefully I found that in reality God was the seeker and I the sought. -Bayazid al-Bastami