How would you know if you had a tampon stuck in you?

There is a chance that it could be sideways up against the wall of your vagina and you aren't feeling high enough. The tampon can't actually go anywhere past your vagina because your cervix won't allow it to pass through. If you really think that you left one up there, I would seek medical attention. All they will do is put a speculum in your vagina and look to see if they find anything. If you decide to wait it out, some symptoms that it may be up there is a very strong odor. If you develop a fever, nausea/vomiting, or a rash, seek medical treatment IMMEDIATELY because you may have toxic shock syndrome, which occurs sometimes if a tampon is left in too long. This can be fatal, so it may be best to go and check anyways. The doctors are happy that you come in rather than wait and it turn into something worse.