How can I have all these symptoms and a negative test?

My last period was April 24th. I had unprotected sex on May 8th. I had very light pink bleeding for a day on May 14th. My breasts are swollen, I have unbelievable headaches (which I never get), I have been extremely tired and I could start crying at the drop of a hat lately. I was cramping for almost 3 weeks straight (making room?) On June 7th I started bleeding a little and still am. However there is no cramps with this blood and it is not even enough to fill one panty liner for the entire day. It is also dark red or brown. Today I have lower abdominal pain (round ligaments?) The downer to this story is that I have had 4 negative hpts!!!!! Could I still be pregnant?!?!?