I'm not sure if this is diastisis recti. If so, how would I go about fixing it? I'm 5'2 and 145 lbs. (photo)

My stomach has always looked 3 or 4 months pregnant after I had a 9lb baby. But after I had my sigmoid colon removed, The doctor used a vertical cut through my navel and the protruding stomach has gotten worse. Now I look several months pregnant. Is this just fat or do I need a tummy tuck?

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