Hey Alaine. Have you tried sitting down together (outside the bedroom) and mentioning how you feel and seeing if there is anything causing his drive to have dropped low? Like stress, illness, worrying about something?
It might be hard to tempt him with all of the things you describe if there is something going on in his mind that is stopping him from wanting to get intimate. It might be worth finding out if there is anything, so you can work on it together (A problem shared and all that)
Just want to point out that the things you have described are all focused on your image. (New undies, sleeping naked, new diet) but it is not that common for a partners sex drive to lower due to their image of you. In other words, it usually has nothing to do with how you look. They fancy you, they got with you because they fancied you and often when we are in love, our partner can change (Put on a big of weight, get grey hairs, see you without makeup...all that stuff) but they still fancy you because "It's you" and they love/care/lust after you. Usually dramatic changes in sex drive are caused by things like worry or stress or exhaustion etc. Of course, it is possible to be caused by resentments too, or falling out of love, but usually you would know this was happening as the dismissal and lack of intimacy and affection and communication would spread to every aspect of your life, not just the bedroom.
It might be worth finding out what is on his mind. If this were me, i'd be asking questions around about now, trying to find out whats changed.
Also, I understand where you are coming from and what you feel. (The upset and hurt) In fact I even wrote a blog post in relation to this, because I have been there and was there for ten years! lol You can read if you like:
It may help to know there are others who went through the same. xx