Implantation Bleeding, Ectopic Pregnancy, Or Just Pill Period?

For the past 2 weeks I've felt a little nausea every time I eat, but never have gotten sick. I also have taken a few pregnancy tests and they all came out negative. I'm using seasonique birth control, and having protected sex, but I guess I'm just a little paranoid because of my recent weird stomach habits. I just got the "seasonique period" this week because I've taken the yellow pills, and it's a brownish/black color and clumpy, and very light flow wise, but it's only the 1st day I've had this light period and some light cramping. I was wondering if this sounds more like a light pill period or implantation bleedings, or even an ectopic pregnancy since the tests came out negative (because ectopic pregnancies have low pregnancy hormone levels, but cause pregnancy symptoms.) Help!