Never heard the term ub-drop, but i recognize the behavior . In the short run, he can be led to believe that his suffering and/or orgasm are a positive and valued things. He should preserve his sperm from (otherwise ruined?) orgasms, and deliver the sperm to you, or consume it himself during a later session. His suffering, pain, willingness to undergo torture, abuse, and punishment should be contemporaneously praised at the moment you inflict it ... your praise and approval should not be withheld to aftercare. The purpose of aftercare, after all, is to bring the sub BACK from subspace so that he or she can at least walk, drive a car, and finish the grocery shopping without danger or embarassment. Re-regression, so to speak.
I beleive that at the core of every sub/slave/massochist is an abuse survivor. If he is rejecting his own proclivities, he may be encouraged to examine his deep past, and to consciously recall the abuse he suffered. His sexuality is the result of an extraordinary aspect of the human mind. The human mind can translate age-old memories of pain, trauma, and abuse into current experiences of intense sexual pleasure. Is he not pleased that his traumatic recollection have yielded a person who orgasms on command, rather than one who pulls the wings off flies, or sets stray cats on fire? Traumatic memories will exercise themselves, and will not be denied.
Finally, remember this: I'm not a real doctor, I just play one on TVs.