Anyone had experience with freaking out over the thought of sex?

I come from a somewhat conservative background, and I think it has affected what I think of sex. I have always been single (23 now) and everytime I am getting along and dating a guy, as soon as they mention sex (even if it is not them suggesting it there and then) it makes me very anxious and I freak out a little bit inside?(and I am a virgin by choice so far)

Has anyone ever had this? I keep thinking maybe I just want to wait until marriage (which is something I'd prefer) but I don't know why I'm still scared of it? Is this normal?