First of all, I'm so sorry for your hurt. I hear you saying the things you are doing and saying and yes, you seem like you're a little too nice, getting scared of another fight, etc., but I commend you for really trying. Esp. the purchase of books, videos, doing things that are romantic, your most recent explanation to her, all sounds like you're a....well...NICE GUY! I might get flamed for saying this, but I can actually imagine how she is feeling. I don't know that I really can help you, but I have been her. Now, this was NOT 6 weeks into a marriage, but more like 10 years, and we also had our moments in our first 2 years (like you guys) where I was just feeling tied down and dumped my then boyfriend/now husband. I'm sorry she rejected you on your birthday. That sounds pretty bad. She was hoping the meal and the gift would show you she cares but she's having a very hard time not feeling like the sex is...I don't know how to describe it, kind of dirty?? Somewhere she is not feeling the love or you are annoying her and her attitude has done a 180 from the "teddy and thigh highs" stage.
I don't post a whole lot anymore, but lurk more than I post, so if I can help, I'd love to, but I would keep talking to her. I would definitely get counseling, maybe a situation where you each have individual sessions as well as joint sessions. I doubt she'll be really honest if you're sitting right there.
Best of luck to you, you sound like a great husband and you definitely deserve to be happy, so try the 180, don't bring it up and make her feel good by being as genuinely sweet and thoughtful to her as you can, I'd say for 2-3 weeks, at least. TRY REALLY HARD not to get resentful and let it show through.