Help needed for chastity

I need advice for chastity cages. My balls keep slipping out. I got several ring sizes and some hurt to wear. I tried a 50mm and it still hurt but my balls keep slipping out. One is smaller than the other and always eventually slips out. Today both balls slipped out. I really don't think it is just a case of going up or down a ring size. Has anyone else had balls slipping through their cage. I really want to wear chastity but I am struggling. Any advice appreciated.