Pelvic Pain/sensation Just Before Period

[wild-bee]

progesterone has all but eliminated my menstrual cramps (woo-hoo) however more and more often recently I get a weird dull throbbing sensation like toothache somewhere around the lower pelvic bones a few hours before I start my period. It doesn't last very long, less than an hour and doesn't particularly hurt but feels very odd, I wondered if anyone has experienced something like this and could shed some light on possible causes