Cramps but no period?

For at least 5 days now i have been experiencing cramps. usually i take this as a sign i'm about to start my period but it hasn't come yet so i am worried. I read online that cramps but no period is an early sigh of pregnancy. the only thing easing my mind is that i took a plan b last month, got the initial bleeding, and i read that the 2nd period after may be delayed. but that doesn't explain the cramps i'm having. help:(