How to let my boyfriend know he can go farther?

I'm not really interested in having intercourse with my boyfriend yet, but I'm definitely up for a little messing around. The only thing is that my super sweet boyfriend is so respectful and will apologize for 3 days straight if he accidentally touches my butt. I keep telling him its okay buy for some reason he always feels guilty. When we make out he'll grab my waist but never goes higher/lower. I've pulled his hands up to my boobs before and he seemed into it but he never initiates contact on his own. I think he lets me initiate everything so he doesn't accidentally go to far. The problem is, I don't know what's too far for him! I feel like if I start taking off his shirt or unbuttoning his pants, things could go really wrong! He's just so hard to read! I don't really want to straight up ask them though, I feel like that's kind of corny and ruins the point.