"Postcoitus" is a bit odd, very clinical and only works for a brief period of time immediately after sexual intercourse. Since it's a technical term, it's worth noting that the formative word, "Coitus" strictly refers to the act that involves both male and female genitalia. Considering the preceding factors, it applications may be of limited use in amorous writing. However, excepting the adjective adjective form "Postcoital", it's the only such word I can bring to mind now that uncompromisingly refers to the period after the act and nothing else.
The above reference links are to to the The Free Dictionary by Farlex, which cites:
postcoitus/coitus. (n.d.) The American Heritage® Medical Dictionary. (2007)
postcoital. (n.d.) Collins English Dictionary – Complete and Unabridged. (1991, 1994, 1998, 2000, 2003)