Recently I've Become Obsessed with Quick-Passing Articles About Women Wearing Men's Clothes! ! !

I want to find that book of quick travel where the female character wears the male character. I remember a dimension where the female protagonist was transported into an egg and she was still a male baby. The male protagonist took it back and took care of it personally. I thought it was very interesting at the time but I can't find it now. Please help me find it.