Some frustrating ones I often come across:
Myth: Large breasts are large because they are filled with milk, like a waterbed. Many men do not seem to understand that breasts are not hollow sacs, and that they are made of fat. Women do not just have milk in their breasts unless they are lactating, and women with large breasts will not necessarily lactate any more that women with small breasts.
Myth: You can fit anything in to your anus right now, don't worry if it hurts - you can take it. While the anus can be trained to stretch out after a period of time, it does take a while. Your sphincter can be ripped, torn, or have microabrasions if you force anything in to it. While it may only take a few days or a week or two to train your anus to be larger, if you try to make a woman force something too large in to her rectum, she could actually injure herself. (This is all also true for the vagina - but my understanding is the vagina is much more stretchy and durable, and can take 'upgrades' in size much better than the anus)
Myth: Once you have trained your anus to a certain size, it will remain that way forever. I have been called a liar and met with disbelief when I told members that I could do anal with bigger toys once, but not anymore. I have been told, "that is counterintuitive." Your sphincter is a ring of muscles who's only purpose is to be tight. When you run a mile in 6 minutes in high school, does that mean you will be able to run a 6 minute mile forever even if you stop exercising for 5 years? The anus and vagina have a natural state they will return to after a period of time.
Myth: You can fit that entire toy in your mouth, just shove it down your throat. I have an esophagus, as most women do. The esophagus is a damn important part of the body. Sometimes I bruise mine. If I have a very small, slender toy, sometimes I can push it in to my esophagus. However, when I am sucking on a toy two inches in diameter, it is not going to fit down my esophagus - ever. If it did, it would tear my esophagus which would be agonizingly painful and require emergency surgery. Just because there is a slender pipe in the throat does not mean it is safe to cram giant objects down there.
Myth: You can easily direct a woman to orgasm by ______ All women orgasm differently. I have had men direct me to do things that were either A) not pleasing to me at all, or B) literally not simulating my sexual organs, and then after 3 minutes tell me to orgasm. Often, members will direct a woman to put a vibrator on her clitorous or play with her clit and then start telling her to orgasm. I can leave a vibrator on my clitorous for an hour and never climax. If you want to see a woman have an orgasm, tell her "Do whatever you need to cum." If you want to see her do something specific, that is okay too. But don't believe that it is going to make her orgasm just because it worked for someone else.
I feel like I've written your blog for you, sorry! I just get carried away and I like to type. These are the ones that bug me the most
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Okay, this is not exactly a body myth but I thought it might fit in to the theme of your blog. It pisses the bajebus out of me!!
Myth: Women who say they started masturbating or having sex after they were 18 are just shy or embarrassed that they started at a younger age. Most or all women start having sexual experiences at a young age. Many men seem to have the idea that cam models are extremely sexual creatures who started masturbating shortly after birth and started having sex at 12, and camming is the only way we can satisfy our overwhelming carnal urges.
I started masturbating to orgasm when I was 16 and I didn't have sex until I was 18. I know a lot of women were virgins or didn't start having sexual experiences until they were 18 or even later. It is neither odd or uncommon for women to discover their sexuality later on. Don't assume that a model is lying or shy when she says she was sexual later in life. If you need to know that a woman was sexual as a pre-teen to get off, that's your prerogative. But your fetish does not mean every model who doesn't fit your ideal woman is a liar.