I have difficulty responding positively to my partner in sexual intercourse & crampy dark mensuration that drop stains instead of flowing , lasts 1-2d?

Separate issues:: inhibited sexual desire and abnormal cycles: both require GYN evaluation.

Estrogen deficiency?: If you're the right age, you could be entering menopause. Reduced estrogen could both reduce libido and result in reduced mentrual flow. Any abnormal vaginal bleeding or major change in menstruation should be professionally evaluated. See your doctor.