It is very unusual for a man who is 20 yrs old to not have experienced orgasm or ejaculation. That he was able to achieve it with your help is reassuring that he is functionally normal. Probably his libido is low and he does not likes as much sexual activity. Alternatively there is something he has not told you which is interfering with his sexual thoughts. He needs to consult a psychiatrist/ sexologist
to further understand the nature of his problem and have a solution.