A CT is 3D; the T stands for tomographic. Often, contrast will be given during a CT to help define structures much better.
From your description, it sounds like a CT scan is a good idea. You need to know what you are dealing with and a plain X-ray is not giving you, or the doctors, all the information you need.
Other tests frequently ordered to help define the extent of the disease are CT, MRI, bone scan and possibly a PET. Blood tests are also usually needed to assess for anemia and other blood abnormalities