I just found your question and realize that it is time sensitive for you because you were seeking the answer before the doctor visit which is scheduled at 2:20. I will leave you an answer.
You are in the early stage of medical investigation. Typically, an enlarged spleen can be indicative of an underlying problem. Several conditions ranging from infections to liver disease and blood cancers can cause splenomegaly (enlarged spleen). Treatment is aimed at the underlying problem, and that is various diagnostic tests must be done. Yes, the spleen is on the left side of the upper abdomen. The liver is located on the right upper abdomen under the ribs. A fatty liver is not always unusual.
Please let me know how the doctor visit went.