Swollen glands only on left side for over a month tried 3 different antibiotics just started clindamycin no other symptoms could this be serious?

Lymphadenopathy: Swollen glands are not an indication for use of antibiotics without a specific diagnosis and you are likely to do yourself more harm than good by continuing to take these. You need to see a doctor who will clearly establish whether there is a medical problem or these swollen glands are simply the body's reaction to a prior illness.