Hi, My Name Is James. I Am 23 Years Old.

Hi, My name is James. I am 23 years old. Over the past two years, i have been getting a strange swelling on my right submandibular gland. It's soft, painless and has been growing and reducing over that time. I have not cosulted a doctor about it yet because i thought it was something harmless. But it's the fourth time am seeing it and it has started to get me worried. What might it be?