Is Stomach Cramping Due To The Ortho Birth Control Pill?

I just switched from loestrin birth control to the ortho birth control pill last month, i have two questions, is the 7 day reminder pills, mean that's when my period is coming or is that to remind me that after those 7 days my period will arrive. Also my stomach is really cramping today and i'm not on my period is this the side effects of the pill?