Could be. How old are you? If the uterus is reacting to hormones, it could do so on a sporadic basis and the calcifications might hurt if it contracts.
calcium easily could do that, but the thing is, if it is calcium then the deposits may be accumulating to be larger in size. Sometimes these spots do require surgery and given your age and adjustment to changes in hormones more frequent doctor visits are recommended, particularly if there is sporadic pain.