J.B.
I went through this with both of my boys. They hated being kept still for any about of time. I became an expert on changing them while they were standing up, on my lap, in the dark etc. My best advice though would be to stop using his changing table. With all the wiggling and screaming its too stressful and he could fall, so just change him on the floor. I use to keep a little basket of "Special toys" he could only hold while I was changing him. Good Luck