How can i tell if i'm experiencing constipation or period pain?

Normal stool?: 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/benefiber/senokot etc..) if constipation resolves but still crampy, then it is, again, likely your period. Motrin/aleve can help. Consult doc. Good luck.