I thought women could only get pregnant if they were married, I think I actually believed this until I was about 10.
At about this time when some girls at school started telling me about what happened in sex, because their mums had told them about it, and my mum hadn't, I thought they were joking and asked if the two people had to be tied together with ropes or something to keep them in position because I could just not imagine how people's parts of the body could go together! I did not believe it for a long time, probably until I was about 12. I still feel silly about that question I asked the other girls and I think they thought I was pretty stupid.
A childhood belief about sex

others believed things like this
- I used to believe both boys and girls had penises so i thought sex was when they tied them together.Anon
- I used to believe that women could only get pregnant once they were married and it just sort of happened Anon
- I used to believe that all girls one day just became pregnant. Like at some magical age it just happened.— niki
- When I was little I thought girls had "man parts" as well, but it just took longer for them to grow.— person
- I thought that the difference between girls and boys was that girls have teeth.
Anon - I thought that a woman got pregnant kind of like catching a cold, by being around her husband for a long time.— No Name