My c section scar is only just less then 2 years old, so I cannot say that I share this experience. However, I would probably see your Dr. It sounds like this should be investigated. All the best to you.
Is there any overlapping of the skin where your scar is? If you have a skin crease there, you probably have a yeast infection in the crease. If you have a crease, you may want to try a topical antifungal.