I understand how you feel when you we unusual thing happening with your body.
That swelling you are talking about be a of any origin so to know that you need an examination by doctor. For that you need to meet general surgeon if your locality. But the cause if it may be junk food, over straining, constipation, spasm of sphincter, smaller sphincter, repeated infection, consuming less amount of water. These factors above may be one of it is the cause for your current condition. To know the reason as I said a personal consult is a must with general surgeon.