I'm confused! HELP

Cierra • Hey y`all I`m cierra, 21. We have a 3 year old daughter, Scarlett and another due april 24, 2015
I took a pregnancy test today at 12dpo and it came out negative. I used the first response early detection. AF is due to arrive on 3/9. But I have heartburn, nausea , back ache, fatigue, sore breasts. I have had these all week except the heart burn started yesterday . I usually get sore boobs a week or two before AF and cramps the days of. Can it be too early still or should I just expect Aunt Flo?