has bc spread to liver?

what are (is) the definitive test(s) to determine if bc has spread to liver? i am 63.
i have had an ultrasound, negative
ct scan without iodine contrast, negative
blood work liver enzyme, negative
yet...i have many of the symptoms listed online and am terrified.
constipation for 2 months, pain in abdomen..not severe, but enought to be aware of, no appetite, minimal weight loss, and today very itchy skin with no rash.
the GI doc says "dont worry", but i know my body and something is not right. if it isnt bc metastasis to liver, i can relax and sleep and then believe him.
thank you so much.
it is weekend so i cant reach any doctor til monday.

[Cleveland Clinic]

Dear yogasue:  The most common test to determine the possibility of liver metastasis is a CT scan (contrast is more accurate).  Ultrasound and liver enzymes can also increase suspicion of liver metastasis.  The most definitive test  to document cancer spread to liver is a biopsy , however, a biopsy is less helpful for ruling out the possible ( also, a biopsy is usually more helpful when there is a lesion on the scan to direct the biopsy).  You might discuss with your doctor whether a PET scan would be appropriate.  This test identifies areas of hypermetabolic activity.  It is not definitive but could increase suspicion.  A PET scan can be controversial and some insurance companies may not cover it.  Most of the symptoms you describe could be from many things.  Itchy skin from liver metastasis does not usually occur unless the bile duct is blocked or there is extensive disease.  It is usually accompanied by jaundice elevated liver enzymes and bilirubin levels.  You might consider a discussion with your primary care doctor to evaluate other possible causes of your symptoms.