My daughter is almost 4 weeks and she won't let me put her down. In the beginning she would. All of a sudden she refuses. Please help

How is she stopping you? You put her down, she crys for a while, and then figures out she will not get picked up.

I agree with Fr_Chuck. My 4 month old tries to do the same thing to me. I just don't pick him up. I call it letting him "cry it out". I know it sounds terrible, but I am sitting there watching him the whole time, I usually put him in his swing or something. When he figures out I'm not going to pick him up, he usually falls asleep (and sleeps good mind you, having done all that crying:p)

4 weeks, why would you want to put her down? I'm not understanding what you mean? Have you checked to see if her tummy is tight? Maybe she has gas. Or maybe she wants you to hold her until she goes to sleep. I'm sorry, I don't see a thing wrong with rocking a newborn to sleep.
They grow up fast.