I have had 4 back surgeries I’ve been having a lot of pain, especially when I bend forward?

Hi, I am a 35 yr old female. I have had 4 back surgeries first was a laminectomy of l4-5 in 2000, then an artificial disc replacement at same level in 2005. They left the artificial disc in and did a fusion of l4-s1 in 2013, which had to be revised the next day due to 2 of the screws at the l4-5 level being too big. Recently I’ve been having a lot of pain, especially when I bend forward and try to straighten up. So I had an xray and mri done. The xray shows anterolisthesis of l4-l5 of 4.8 mm which increases to 5.3 with extension. My pain doctor referred me to a surgeon, a different one than the one who did the fusion, I did not want to go back to him. He says this type of movement is abnormal. I went back a nd looked at previous xrays, a nd a month after the fusion it shows 3 mm of anterolisthesis with flexion. Why would this have been doing this after the fusion? I noticed it has increased in mm with time. Can anyone give me their opinion on what is going on?