Re: 4 week old will only sleep on me!
another thought - when she sleeps on you, she's on her tummy right? And I assume when you put her down it's on her back? Some babies just plain won't sleep on their backs. My DD only slept on my chest until 4 weeks old (when we gradually transitioned her to in bed beside me), just like you're describing, and, in hindsight, I think it was as much about being on her tummy as being on me. I know on the back is what is recommended, but, for me, with the one I'm growing right now, if she'll only sleep on her belly then belly it is. However, she'll be in the bassinet right beside me so I feel comfortable with that.