how old where you when you were thinking of these things? I didn't know about a period until almost high school
when I was a lad, I thought you could get pregnant from kissing and condoms were made for your tongue... a friend of mine told me that if you pee on the toilet seat and a woman sits down on it, she could get pregnant from getting inside her. I was so concerned when my mom was pregnant with my younger brother that it could have been from me peeing on the seat
I also thought that the vagina was sealed from the outside and "popping a cherry" meant you break the seal... almost like putting a piece of wax paper over the top of an open can. I realized this in middle school when I asked a girl if she had a "vagina" and she punched me in the face
probably the biggest misconception I had was I thought one day I would stop masturbating