Almost two weeks late?!

I'm nine day late (July 4th was my expected period date and I spotted earlier that week just for a day not enough to fill up a panty liner) since then I've taken two first response pregnancy tests ( one the day after my missed period and one yesterday) they were both negative, but I've been having nausea and constipation.  Headaches, moodiness, back ache and lower abdominal cramping....could I still be pregnant even though I've gotten two negative tests? Did I test too early?