What absorbancy are you using? If you're using an absorbancy that's too high for your flow then you're going to to feel it inside you. I know whenever I use a one that's too high for my flow I can always still feel it even if it is pushed in far enough. Have you tried using a lower absorbancy? Though I suppose if you've been trying to use them since you were 13 and you're 17 now then I assume you have tried different brands/absorbancy levels.
Also if you're a virgin then that could have something to do with it. You can use tampons even if you are a virgin; I've been using them long before I ever had sex, however I know someone who couldn't actually use them until after she'd had sex. No matter what brand/absorbancy she used she simply could not get them to work -- she either couldn't get them up properly or she always still felt them inside her. However after she had sex she could use them fine. She thinks because, psychologically, she knew that if something as big as a penis could fit in then something as small as a tampon easily could.