Bleeding from vagina. help?!?

Two days ago I've noticed very small amounts of blood coming out my vagina and it is still happening! I know I'm not on my period. I'm not sure if its coming out the vagina or if its in my discharge. I am not a virgin. Could I maybe pregnant. Me and my bf last had sex the end of April. I been getting my normal periods ever since so I kinda thought pregnancy wasn't it. But is it possible to have your period after having sex and after a lil over a month u start spotting. Right now I'm feeling a little nauseated. I took a pregnancy test yesterday though and it came out to be negative. I only paid $1 for it so maybe its inaccurate?? Tell me what's wrong with me please!?