Let's not talk about sex?

In class today the topic of Pansexuality came up and someone mentioned that sex is a topic that isn't really talked about even though it is everywhere. I must say that I agree, sex is everywhere and it supposedly thought about multiple times throughout the day. It is in movies, magazines, the Internet, and even in books, however to blatantly talk about sex, it doesn't really happen. Sex has always been. and still is an intimate topic. It was said that even during the time that Freud wrote his theories, sex was not a talked about subject. So it made me think, why did he make such a bold move? also where did he get all his sexual references from if sex was not popular? Did he only base it off of his sexual desire?
Another thing I don't understand, is that Freud says that as children, the girls had penis envy and we do not remember having penis envy because we were little. I mean the only reason I would think a girl would have penis envy is because guys can stand up to pee and girls have to sit down or squat. But if we were so little and we didn't even know what penis's were how could we have penis envy. My parents were strict and never knew a male appendage until I was of age to remember my thoughts. Some of his theories seem to be really under-developed.
I also was wondering about something else. You see, I am in this class called Popular Hollywood films of the 1950's and I watched this movie in which the younger man fell for an older woman. How would Freud explain this? Would he say that the man never went through the Oedipus complex and is finally going through it as he is choosing a mate? In the movie he never talked about his mom and only his mom so one can assume she died while he was young. So does having/desiring an older mate connect in anyway to Freud's theories of development?