Have a swollen lymph node behind my left ear for 3 years now. it stays the same size had blood work and ct scans, not on any medications. have ibs?

Lymph node: It is behaving like a benign lymph node and active surveillance is reasonable. If you want peace of mind and eliminate the risk of malignancy, than an excisional biopsy by a general surgeon should be done.

Continue monitoring: Many lymph nodes are palpable in areas of the body where close to the skin surface: behind the ears, along the neck and in the inguinal areas. They may swell in reaction to many causes including infection, inflammation, etc... What you are describing is most likely a reactive lymph node. If it swells over time and increases in size, further workup is warranted.