Check this out with your husband. Get his viewpoint about your son's increased distance from you in this area. Perhaps he needs to share feelings and experience with Dad more right now and with you less. He is the first one to grow up, and you have never seen what independence and separating gradually from Mom can look like before. As he grows you will be needed, but it may take a different form than going through his lessons with him.
All children are unique.
He is expressing a need for greater privacy and independence in this area with you right now. It may be best to simply follow his lead and to support his need for greater autonomy. He may be wanting more identification with his father at this time, and may need to distance from you in order to find his sense of what it means to be male. Maybe handing it over to Dad could be useful. Talk with your husband about your feelings and ask him for help.