Preg or cycle

I've read the early signs of pregnancy. The only signs I get is headaches, and my breast & nipples are sore when I touch them, or squeeze them.Also, cramps & feel nausea through out the day but have not thrown up, i'd be 4 weeks pregnant (if i am) I've had these symptoms before, but started my period. I'm supose to start my period today or on the 13 base in this other app I use called (CLUE). I hope I miss it, & is pregnant! But could I be pregnant? Please help, & give me hope.