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Pain in umbilicus or belly button could be due to abdominal causes or due to a cause in the umbilicus itself. The common abdominal causes are recurrent appendicitis, IBS, Crohn’s disease, umbilical hernia, cystitis or due adhesions if there is a history of previous surgery (as in your case). Causes within the umbilicus include a boil or a fistula or abscess.
Adhesions can only be diagnosed by laparotomy.
Since I cannot examine you and know other related conditions you may be having, nor is a detailed history possible on net, I have listed the various possibilities that should be looked into. Please discuss your PCP for primary examination followed by proper referral.