What Causes Abdominal Pain And Dark Periods?

I am 32 years old married 2.6 months back now we are looking for a bay. my menstrual cycle is 28 or 29 days but this month i didn't get my periods on time but meanwhile we have been to our native place where i undergone few physical activities . may be due to that i got my periods on 32nd day with painfull abdomenand dark i colour so do u suggest me somthing for this