I am the same way! I did hesitantly try a toy my fiance was picked to review for free,Gum Drop Slick
. It didn't hurt me, but it felt.....odd. There was one time where we had a slip while having sex and he went in the wrong hole (lol), I shot up so fast and screamed. It HURT. I'm just really scared. You aren't alone. But there is nothing wrong with being scared or with not ever wanting to try it. If you do want to try it, there are plenty of kits and small toys here that people have used to work their way up to being comfortable with a penis going back there. I just don't think I'm one of those people.
I'm glad my guy doesn't ask or push me to do it. We talked about it once and how I said it was an exit only, he said he would only try it if I wanted to and that he doesn't care either way and is satisfied with our sex life.
This is gross and embarrassing but I'm gonna say it anyways, I'm sure most people have had a bowel movement where it was hard and big in size (lol, I'm blushing typing this) but I thought HELL NO, if something hurts coming out, then I don't want a hard, thicker, penis GOING IN.
I'm perfectly content with vaginal and clitoral pleasure.
You gotta work yourself up to, you have to relax if you want to do it.