6 days late and pregnant?!

So my bf and I had sex about 5 days before my period and now I'm 6 days late , sore nipples(not boobs) overly tired and I few other symptoms that would be normal if I had started my period ....I took pregnancy test when I was about 2 days late but it was negative... but I'm nervous it could have been a false negative?? and today I started light cramping with literally just a few spots of bright red blood! Thoughts??