Confused!!

The last week I've been nauseous off and on, had heartburn, hunger, cramps, had some tiny bit of brown blood after my DH and I did the deed last sat night and I've been tired more then usual. I'm supposed to start AF on Friday. I took a pregnancy test Saturday and got a faint positive, took another today but was negative. Do you think I still have a chance regardless of the negative test? I was so happy seeing that faint line and now I'm upset thinking it was false. Btw both tests were red dye tests.