Hi,
Was your ultrasound just on your stomach or was it also internal (vaginal)? Fibroids can also cause these problems and can be picked up on ultrasound of the uterus.
I would definately wanta CA125 blood test done. Even if your insurance doesn't pay. It might cost about $100. The problem is that it can be elevated if there other problems going on, like fibroids or endometriosis and some other stuff. It is supposed to be used to monitor chemo response. But it is a good starting point and if elevated gives you a direction to look in. And the other person is right, it is not always elevated with cancer.
Also, you NEED at CT of the pelvis and abdomen. If you tell your doctor (primary care or GYN) you are having: fatigue, bloating, abdominal pain, unexplained weight loss, bowel changes, changes in period and ASK for the CT of both pelvis and abdomen they will order it. If they don't - CHANGE DOCTORS. Early treatment can save your life!