I am having period like cramps and back pain 12 days before my next expected period this month. is this normal?i'm 24 years old

Cramps: ovulation ?: Rarely, pituitary hormones will cause two immature eggs to develop, so the estrogen levels are much higher just prior to ovulation. With ovulation, these levels drop suddenly, producing period--like cramps and back pain similar to when your actual period occurs. This also explains why fraternal twins occur with pregnancies happening with two mature eggs.