Your son wants to know what it's like to be a girl. I'll hazard a guess that he's sensitive, interested in relationships in a very basic way and notices people and how they act. I think this is good. He doesn't yet have the experience or words to let you directly know this.
My 4 yo grandson plays with his sister's toys as often as with his own. And just today my 7 yo grandaughter told me that she wants some boy's toys of her own. She's still dealing with sharing.
Her favorite color was pink until this summer. Now it is blue. Her mother's, my daughter's, favorite color was blue while she was growing up. She was a tom boy; didn't like to wear dresses. She loves feminine looking clothes now.
Fifty years ago my male cousin, when he was in grade school, pleaded for a doll. His father said "no way." His mother bought him one anyway. He only played with it out of site of his father. He and I had great fun playing dolls. He is definitely heterosexual.
A part of healthy development is for kids to try out different things. That is the way that they eventually learn what the world is like and who they are. This process takes years. Actually some kids grow up without knowing who they are or even who they want to be. This is sad.
This process does not determine gender identity.
I predict that this is a phase. If you accept his ideas he'll move on to something else. If you have a negative reaction to his choices he may cling to them. Your acceptance or criticism will affect his self-esteem. My cousin thinks that he has no worth. Of course his father was stern and critical in a lot of areas. And that was not your question.
It does seem that your son is going all out in the direction of girly things. Perhaps he sees ads or programs on TV that have sparked his interest. Does he have a friend who is a girl and he wants to be like her? Maybe he's identifying with you, his mother. This is one of the normal stages of development.
I wouldn't worry, if I were you. He is "normal."