You had an anterior approach to the spine. An incision on the left requires cutting some abdominal muscles and these muscles will not heal and function as before the surgery. This abdominal wall weakness has two separate consequences.
One is that the opposite side muscle will continue to pull with regular strength and the surgical side muscles will have less “pull” (strength is diminished by the incision). This imbalance will pull the midline off center (as marked by the umbilicus or navel).
The second consequence is that the abdominal wall on that side will bulge somewhat with the complaint of “bloating”.
“Core” therapy work to try and rebalance the abdominal wall may yield some symptom relief. Make sure you have a consult with the original general surgeon who made the initial incision and approach to make sure there is nothing wrong (abdominal wall hernia).