Thank you for the compliment.

Hargashah is not well defined in written halachic sources. A number of possibilities are described 1) she feels her uterus open, 2) she feels her whole body shake, and 3) she feels an internal flow. Based on discussion with women, there are very few women who experience the first two (but, at least for the first, they do exist). The third one is reported by a greater number, although often in the middle of a menstrual period rather than at the beginning.

Different authorities take different approaches to the apparent rarity of hargashah today. One approach is to state that hargashot no longer exist. Therefore, if a woman thinks she has one, she is probably mistaken. Another approach is the opposite; most women do hav hargashot. Therefore, if a woman says she does not, she in fact probably does but is not aware of it. Our approach is a middle ground. We try to assure that the sensation the woman describes fits into the halachic category of hargashah and not veset haguf (see articles for more details). If she does report that she experienced a hargashah, we assume she is correct.

Due to the overall rarity of real hargashah, our tendency would be to say that if she is not sure, she probably did not experience one (except in cases where the halacha assumes she did, such as after bedikot, marital relations o urination).

The above is a general summary. Each situation has to be judged individually.