Does Back Pain And Delayed Period Indicate Sign Of Pregnancy?

hello.. my last period started jan 20 and ended the 24. it is always 28 days. expect in jan it was suppose to start the 12.so it was late. my fiancee and i have been trying to get pregnant.i have been extremly sensitve this month(crying for no reason).this month i still havent started my period. my lower back hurts like it does every month.i have been getting lil headaches for a bout a week now..can i be pregnant?