I would tend to snap back somehting along the lines of 'What are you a fashion commentator?' Not very professional though. You should probably say something along the lines of 'it makes me uncomfertable when you comment about what Im wearing' although if youre like me and non confrontaional it can be hard, maybe you could change the 'you; in that sentence to 'people'. I hope you can resolve this quickly and start feeling more comfertable at work