Hi, first day of my last period was January 1st, I had unprotected sex on the 18th and 19th...this past week i have been experiancing constant head aches, cramping ( like period cramps ) , back ache and sore breasts...my period is not due til January 31st, I am very consistent with my periods they are always right on...could this be sign of pregnancy or is it way to early to tell?