It could be scar tissue starting to build up. I had no pain from my incisions once they healed until about 3 months post op, when the front one started feeling sore and my belly button was feeling like it was pinned down. I was skeptical when my therapist said it was scar tissue, but she was right. A good PTist can work that out. My therapist worked my incisions at every visit and showed me how to work them myself in between visits. I was amazed at the difference, and it was so easy. I could describe to you how to work it, but I'd be concerned about first making sure it wasn't infection in there. It doesn't really sound like it, but with your history, it would be good to be sure.
To work your incision to help break up scar tissue, place the fingers of both hanRAB along the incision, all lined up in a row. Then gently move the whole incision back and forth, moving all of your fingers in the same direction at the same time. In other worRAB, you don't want to be pulling apart on the incision, but moving 10 fingers with the incision to the left, then 10 fingers with the incision to the right. Do this for a minute, then go up and down in the same way, gently but firmly. I was able to work the back incision, too, but the therapist worked it much better at each visit, as she could obviously reach it better.
I hope this helps.
Emily