Why does it hurt to insert a tampon?

Ohkaay, so ive had my period about 5 times and ive been using tampons for them for my last 2 periods. When i put the applicator in, i feel a tiny bit of pressure. Then, as soon as i go to push the smaller part of the applicator in so it pushes the tampon in place, it hurts SO BAD. Likee, it feels like a lot of pressure and like its rubbing the wrong way or something i cannt really describe it but it KILLS. But as soon as im done, i dont feel a thing. After that im finee. But why does it hurt when i push it in all the wayy? Im not putting it i. Straight up, im doing it like your supossed to, tilted towards the small of your back. Oh, and i use a regular absorbancy, and i have a light period i guess. Im thinking about getting slimmer tampons. Could that help my problem?