It is usually very frustrating when there are symptoms but all labs are normal. On the other hand, normal labs are encouraging, indicating major body systems are functioning well despite whatever process may be going on. We do not know you medical history, family history, social history or travel history. The episodes you described, as you mentioned, do not clearly point to a specific diagnosis. If we were to only go by US findings of liver, and intermittent chills plus a variety of vague symptoms:

Unusual causes of paranchymal liver disease on imaging may include metabolic disorders like Hemochromatosis or Wilson's disease or Autoimmune disease. Earlier stages could be hard to diagnose. Dr Vupalanchi is a good hepatologist at St Vincent Hospital.
When dealing with fluctuating unexplained chronic symptoms it may be appropriate to evaluate your home and work environment for potential exposure to toxins through water, air vents, car, medications, partners or food. Your travel history may have exposed you to diseases doctors in Indiana do not look for, like malaria that can cause intermittent chills. About 12 years ago it affected a number of people in Chicago. Ask your primary provider for related testing or consider consulting an Infectious disease specialist for chronic viruses that my reactivate causing vague symptoms including chills like ebv. Lyme and Erlichiosis disease may be hard to diagnose. Lyme antibody will be negative for many weeks after an infection so early negative labs may be false. Since you live in Indiana, consider seeing Dr Misra at IU, infectious disease.
Dr Imad Shawa is an internist/pulmonologist/critical care doctor affiliated with st Francis Hospital in Indiana. He is very experienced in work up of complicated or unusual cases. However he primarily sees pulmonary patients in private practice.
If no clear diagnosis is made, an option is to optimize healing ability of your own body by trying a "lifestyle medicine program" while you continue your search Avoid alcohol to protect your liver. Best wishes.