Hello and welcome to eHealth forum!
In your case it can be the persisting mono infection. Swollen lymph nodes across multiple areas or generalized lymphadenopathy can also be due to viral infections such as cytomegalovirus or due to bacterial infections like TB. HIV or AIDS, leukemia, lymphomas and other cancers can also be a cause. This could also be due to inflammatory conditions such as rheumatoid arthritis. Since you also have rash like lesions rheumatoid arthritis and bone marrow disorders need to be ruled out.
It is difficult to determine the cause on net. This is not something you should ignore. Please consult your doctor. Take care!