How to tell a guy I'm going on dates with that I don't feel ready for physical stuff just yet?

I had a very very bad physical experience with a number of men when I was 16. Because of this I dislike physically sexual contact even kissing when I don't know someone very well.

I've been friends with this guy for a year and been on one date with him but he's very physical and has invited me over to his tomorrow night. I know he wants sex.

How do I explain to him that I am interested I just feel uncomfortable being this physical with him this early on without having to talk about my traumatic past?
How to tell a guy I'm going on dates with that I don't feel ready for physical stuff just yet?
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