It sounds like it might be getting caught on your hymen. Most girls tear their hymens around puberty from running, jumping, masturbating, and using tampons. Some hymens are more durable though, so they don't break as easily. That means it might cause you some pain and discomfort when you use tampons or have sex. If it proves to be a real problem, talk to an ob-gyn about it. Some hymens are so tough that the doctor actually has to cut them.

More information: http://www.coolnurse.com/hymen.htm

yes, it sounds to me like this is your hymen, too.