I had intercourse and then took my last active birth control pill (before placebos). i am experiencing light cramping. could i be pregnant?

Maybe: probably just some premestrual cramping, but never a bad idea to check a pregnancy test.

Unlikely: If your body has been stable on this "pill" for a while, it protects you on active and inactive pills. Pregnancy signs also take a while to begin, starting as early as when you might miss your period. Pee tests are cheep so you can always do a couple.