Lower left rib cage is englarged and sometime painful I have have not really been hungry all day and tired....I live by myself and don't know what to do

While . While it is not possible to give you a full answer without examining you, i would be concerned about an enlarged spleen. Patients with mononucleosis can have fatigue (being tired), decreased hunger and an enlarged spleen (under your left ribcage). I suggest that you contact your primary care doctor to examine you and do appropriate lab tests. Mononucleosis is contagious and an enlarged spleen can be injured or rupture.