A childhood belief about periods

My parents never were (and still aren't) the kind to make one feel real comfortable talking about a lot of things with them. So, as a little girl when I first heard of menstruation as something girls would grow up to have, I was very curious but had no inclination to ask my parents about it. Instead, I asked the closest person to me at the time, an uncle, who isan't as much older than I as you'd tend to suspect from his being my uncle. At first he was reluctant and asked me why I didn't ask my mother about this matter. I treid to explain that I wasn't comfortable talking to her. Finally, what he opted to do was check out a library book on the subject, written for young girls, and have us read it together, with him helping me with "big" words and the like. As that made him open up on the subject, I found he really knew a great deal about it after all. He told me a bunch more than was in the book. All of it turned out to be accurate except one thing. He told me that when girls start menstruating, that takes the place of pooping so that they don't poop anymore. Later when I started menstruating but continued pooping, I was distressed and thinking something was bad wrong with me. Finding out the truth made me mad at my uncle for years. But he in time would convince me that he told me what he honestly believed at the time, and now we're friends again. I've found out that his big sister put a lot of crazy ideas in his head. He doesn't remember whether that was one of them or not. But I consider it a safe bet that it was. Safe enough that you can guess who my least favorite aunt is!