Experiencing a dull ache on the lower right side of my abdomen?

I have been experiencing a dull ache on the lower right side of my abdomen. It has been around for a few years, and it comes and goes. It feels like a very dull pain, or a burning sensation. It doesn’t feel swollen. Touching the affected area doesn’t hurt, I really have to press on it to feel the pain. I don’t have a fever, or nausea. I provided a picture and marked where I feel the pain.

I have noticed that I get this ache when my menstruation is about to start. I’m due to begin any day. I’m just hoping it’s not something serious like appendicitis. Thank you.

Age: 34
Female
Medications: No medications
General Information: I haven’t seen a doctor about it.