Pregnant, Cyst or Ovarian cancer?

On April 1st I started what I thought was my period but it only lasted one day. The second and third day was just a spotting. I have taken 4 HPT all were negative. I have cramping and a great deal of abdominal swelling, bloating,really gy and I just can't seem to fit into my clothes. If I were pregnant it would only be 4 weeks but that is to early to have gained weight and have this much bloating. I have had spouts of diarrhea I am actualy moving my bowels even though I normally do not. I went to the MD today they did not do a pregnancy test since all mine were negative but i go for an abdominal and a transl ultrasound tomorrow and must say i am really worried. any thoughts as to what could be happening to me?