What Causes Swelling Of Abdomen After Disc Removal In Lower Back?

I had a disc removed in my lwer back and then fused with cage and screws in Oct last year. They went in thru the front to do this. I woke up with a swollen belly they told me this was normal swelling. I ve had months of PT and can tighten these abdominal muscles but they protrude outward making me look like I swallowed a mellon. that is my stomaches constant shape. The muscles feel hard but start at the pubis going up. They sart out flat for a few inches the right angle outward and then curve up and around to form my ballon belly although these muscle are hard I don t think this is the correct shape and that something is not right