<human>: I am a 23 year old female grad student. Since July my right lymph node in my bikini area swells up randomly. It swells up to about the size of a lima bean, or a small grape, and it's very painful to walk, wear pants, and even wear underwear because it rubs up against it. 

I have been to a walk in clinic (like CareNow) twice now for this. Both times I was given an antibiotic, had a urine analysis and sent on my way. All tests were negative. I never feel sick or ill when this happens. The prescribed antibiotic helps reduce swelling and pain of the lymph node, but it always comes back within a couple months or so. I have tried drinking Emergen-C and vitamins but that doesn't help. 

Is this a sign of any underlying conditions? 
I feel relatively well. The only thing that's different (that I can tell) is a fatty mass on the right side of my lower back. I've had this mass since I was 12 years old with no issues. However, recently it's been painful. Not sure if this is related or not. 

Going to a GP is not an option due to insurance reasons. I only have access to walk in clinics in Oklahoma.

Summarize the given text in a few sentences.
<bot>: 23 year old female has a chronic swollen lymph node. Antibiotics help in the moment but the node swells back up after a few months. Urine tests have all been negative. What could this be?