I think people are being way too hard on this guy.
He sounds like a lonely guy and doesn't have much experience with women (something I can totally relate to, I spent the vast majority of my adult life alone and unwanted.) The clothes may be all he has ever had and that is how he learned to arouse himself, and once that is ingrained it is tough to re-learn something else. It is how his mind may be wired, and it does not have anything to do with you and how attractive you are etc., it is how he learned to become aroused. GGs often have a hard time understanding this. He could very well love you and want to be with you, and his interest in the clothing etc. alone does not mean he does not love you or want to be with you. Men learn how to be aroused at a very early age and the fact he finds the clothes a turn on started long before he met you, and we don't get to choose what turns us on. It is in no way a reflection of you.