Repairs MTD / Yard Machine Edger 3.5 HSP Keeps destroying belts

I have a 3.5 HSP MTD/Yard Machine Edger that i have had for approx. 15+ years, this year i noticed that the belt was getting a little loose, so i bought a new one and installed it, during the second time edging my yard i noticed that the belt was fraying a little and i noticed that the belt had turned itself upside down, so i took it off and trim the frays then went back to edging, then the belt flipped upside down again and really went to fraying apart. So i thought i must have bought a bad belt and went to purchase another one, mind you that the original belt was 15+ years no problems, the new belt cost $24 and lasted 2 weeks, the second belt did the exact same thing that the other belt did, so it lasted 2 weeks and another $24, so now i am stumped and $50 later with no belt. Please help....any ideas??? before i go buy another $24 belt, if i keep this up i could have bought another entire edger for what i have spent on belts alone.