Is adenomyosis always painful?

Usually. Adenomyosis is essentially an invasion of the muscle layer of the uterus with lining cells of the uterine cavity. One is essentially having a period inside the muscle walls. Early on, there may be negligible pain but by and large it is painful with heavy menses, cramping and hemorrhage. It usually ends with a hysterectomy.
See below. Adenomyosis is uterine thickening that occurs when endometrial tissue, which normally lines the uterus, moves into the outer muscular walls of the uterus. Symptoms: •long-term or heavy menstrual bleeding •painful menstruation , which gets increasing worse •pelvic pain during intercourse note: in many cases, the woman may not have any symptoms.