Thanks for your query.
Pain abdomen just before menstruation
is normal and is called primary dysmenorrhea.
Pain abdomen one week before periods is something to be of concern.
Usually Pills reduce the amount of menstrual blood and hence dysmenorrhea.
You need to consult your Gynecologist to rule out secondary causes of dysmenorrhea like endometriosis
Take NSAID's for symptomatic relief. Get a trans-vaginal USG for diagnosis.
Hope this helps.