I would say too this is not right. If it goes back in everytime I would say it might not be a prolasped but perhaps might need a stitch in there to keep it tighter. I have heard of this needing to happen...more so in iguanas but snakes need this at times as well. Other than that.....she might have a bacterial infection or a parasite overload.
Take him to the vet and see what they say.