birth control side effects or pregnant?

please help!!!

so im 7 days away from my period and im experiencing mild cramping and a sore back. im on the combination pill and take it at the same time every day. ive been on it for 6 months now. 13 days ago my bf and i had sex and he did not pull out twice. are my symptoms just due to pms/my pills or it means something else? thanks!