I read a book as a teenager and I am trying to figure out what the title is. All I remember is that the woman in the story wanted to have a baby and ended up having twins with a long time friend. The most memorable part was that they had sort of like a deal that when she became pregnant, she would let him know by putting a windsock outside the window. He lived next door, I believe. Please, I am desperate. I've been looking for this book for almost 30 years! All help is appreciated.