My infected knee implant was removed (fifth time) replaced with temporary knee insert 5 years ago. The insert has moved. The insert is painful and wearing me down. I can't put weight on that leg. I have been unable to face full knee surgery again. I g

Very tough situation. Unfortunately, if the spacer has moved, it will continue to move and erode bone. Since you are young, some options may include repeat knee replacement (assuming the infection has been eradicated) or fusion, in which the knee is made stiff. People can usually walk with a fusion, with minimal pain; however, sitting is difficult because the knee doesn't bend.
Having. Having had four infections after replacement would put you at high risk for subsequent infections....Have you and your doctor considered a knee fusion (making the knee stiff). While the knee wouldn't be able to bend, it could support your weight and typically is not painful. However, if you are determined to go through revision knee replacement and your knee no longer shows signs of infection there is probably a chance that it could be successful..