Thanks for your question and concern. If you are using the tampons in a correct manner then it will definitely not cause any kind of sexual infection or disease. Tampons are a cotton product that fit into your vagina completely that helps absorbing the blood during the menses before it flows out of vagina. You can insert tampons into your vagina using some applicator or it can also be done using your finger. There are various types of tampons available in different sizes. The packets containing tampons have complete instructions mentioned on them for the correct usage such as how you should insert them into your vagina and then probably how to remove them. Once you insert a tampon into your vagina, you will not be able to feel it and a string attached to it helps its removal. You can also use tampons even if you never had sex with your partner. All you need to take care of is about the way you insert the tampon into your vagina so that it does not causes any kind of discomfort. Before you start inserting the tampon into your vagina, you should be in a very comfortable position and must be feeling relaxed for inserting it properly. It is not inserted properly; you can remove and try inserting it again. A properly inserted tampon will not be sensitive. So there will not be any STD symptoms linked with the proper usage of tampon. Still, if you are worried then you should probably visit your local doctor and gain the knowledge about all possible STD symptoms that can be associated with the improper usage of tampons. Best wishes.