You should never ignore any stomach-related aches and irregularities, as they can be due to serious irregularities in your internal organs.
Being a woman some of the possible causes of your continuous stomach ache can be -
Menstruation.
Result of a miscarriage.
Ectopic pregnancy
Issues of fibroids and some other pelvic diseases (inflammatory).
The best thing to do will be to consult a medical professional as soon as possible.