I have great news for you: You can't put a tampon "too far" in! And a tampon can't get lost inside you, either. If your tampon has a string, it will be really easy to just pull out. If your tampon doesn't have a string, you'll be able to reach it easily. So don't panic about your tampon getting lost in your nether regions -- It's not physically possible!
It is going to be okay. Your vaginal opening isn’t even long enough for the string to get lost so you will always have that assurance that it can be pulled out. Many of us have had the same worry. If there comes a time, where you do not see the string, you need to try to gently pull it out. Wash your hands, clip those nails, and gently search for the string. On rare occasions, some have not been able to find string to pull it out. I have shared the story before of my friend who could not get the tampon on her own. She called her doctor and went in and they got it out, painlessly.
Knowledge is power, and the more you know about your body the more comfortable and confident you will become! Look at pictures, learn your anatomy, even try sitting on a mirror to see yourself better. Know that a tampon can’t get too far up. Why? Because your vaginal canal is approximately eight centimeters in length and dead ends at your cervix (the end of your uterus). If for some reason you cannot find a tampon string, simply inserting a finger or two should help you locate it to pull it out. To be more specific, wash your hands first, sit on the toilet or lay on you back with your knees bent up. Consider using a mirror to see what you are doing. Using one or two fingers, apply gentle pressure right at the vaginal opening. Your fingers should easily slide in and be able to feel any foreign body such as a tampon. If you can indeed reach all the way up you may touch your cervix which is a round puffy non-tender organ. None of this should be uncomfortable. The first time, this whole thing may seem a bit awkward, but soon enough you will become more and more comfortable.
Actually it can happen. Especially when the pull out thread slips in. There is no way to get the tampon out when that happens. I had to go to the OBGYN 2x to get it removed.
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