Swelling Around Csection Scar

I have had two c-sections the last was two years ago. I have noticed since that at times I get swollen areas around the scar whitch look like a ball shape under the skin. Normaly they are either on the right end or left end of the scar. They hurt a little but mainly cause an itching sensation. I notice them most often after I have been sexualy active. Any one ever have this happen before? Help!