How to respond when your new boyfriend says he loves you?

So I'm sure this happens a lot, but I thought I'd ask a fresh question. Me and this guy have been going out for a month now, and I *really* like him, but I'm sure you can understand why I wouldn't be ready for that uh, level, yet.

I'm only fifteen, and he's sixteen, we're both in year eleven at school and he's said he loves me twice this week. I admit he says it sort of casually, but I still feel bad not saying anything back. I'll just smile and hug him or something. I've promised myself that I won't do or say anything until I'm ready to do so, and I can see myself loving him in the future. I just think right now is too early in the relationship for that sort of thing, not to mention our emotional maturity.

Also considering our ages and the amount of time we've been together I highly doubt he actually "loves" me, which is fine, I would just like to respond nicely when he says it to me. Obviously I couldn't say something like "and I really like you", but then what *do* I say?