back in the saddle; back in the saddle again adjective experiencing the bleed period of the menstrual cycle US, 1954
— Frederic G. Cassidy, DictionaryofAmericanRegionalEnglish, p. 120, 1985
When I was a teen and the common protection consisted of the elastic sanitary belt and pad, we referred to being “Back in the saddle again.” — a contributor TheMuseumofMenstruationandWomen’sHealth, April 2001