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?