Does Menstruation Delaying Medication Cause Irregular Menstrual Bleeding?

Hi Im married and i was on a period delaying pill called "Meprate" for 15 days prescribed by ny doctor. I have regular periods occuring at a gap of 28 days. I took the pill rom March 12 to Mar 23 and on Mar 24 I got my periods. Again I got my periods on April 6 th(a 12 day gap only), but the bleeding was too minimal. Kindly advise why this has happened so...