If your stool is normal and the frequency is same as usual, and you experience cramp during/around your period, then it is likely your period.
If u have constipation
, then treat it--increase fluid, add fibers (fibercon/metamucil
etc..) if constipation resolves but still crampy, then it is, again, likely your period. Motrin
can help. Consult doc. Good luck.