What Causes Movable Lump In Lower Abdomen?

Hi, may I answer your health queries right now ? Please type your query here...I'm a 28 year old female who had a c-section 2 years ago. Within the last few months I have noticed a lump in my lower right abdomen. It is not painful and I only notice it when I am laying flat on my back. It moves from my lower right side to around my belly button. When I feel of it it usually disappears. What could this be?