Cramps but no period

I usually get my period in a certain spot of my birth control pack well it hasn't come this time i always cramp a few days before my period well this time I've been getting cramps on and off but its a week after where I usually get my period. My dr recently switched my birth control but she has switched it before and it never effected my period. Could this be a sign of pregnancy? Or is it more likely becasue of the bc being switched. Did anyone cramp when they found out they were pregnant?