What Causes Pain And Redness In Old Scar Of Hysterectomy?

I am 53 years old. I had a radical hysterectomy in 1986 for endometreosis. I have recently gained 20 pounds and I can't hold in my stomach any longer. I swam yesterday for exercise and when I showered felt an intense burning sensation at the old scar where my belly now protrudes. I am desperately trying to lose weight, but what can I do now for the pain. The scar is red. I never had any complications. Could adhesions cause weight gain?