"Sleeping together" ment the man and the women would fall asleep with out any cloths. If the mans willy touched the slit between the legs she got pregnat. Unprotected sex was when one or both forgot to put their underwair back on before they went to sleep.
A childhood belief about reproduction

others believed things like this
- I was told that if you sleep on your back you swallow your tongue...I have been sleeping on my side ever since— scotty la
- Yeah I believed (because my mother had told me) that your 'willy' would fall off if you played with it :D— Doz
- i used to believe that when you did the splits your legs would fall off.Anon
- When I was a child i used to believe that if i did not fall asleep an elf would come for me Anon
- I used to think that when my arm would fall asleep that it was raining inside my armAnon
- If you undo your belly-button with a screwdriver, your legs will fall off.— Toby