Why can't I put in tampons?

Yo

I've tried putting them in at least 4 or 5 times but I can't get them to go in. I exhale and relax the muscles as I try to push it in, but it goes maybe half a centimeter and then it just starts hurting a lot. And then I feel really bad because I wasted so many tampons. Does anyone know why I can't get them in? I'm a 14 year old virgin if that affects anything.