What should I say to this boy?

So me and this boy have only been talking for about 3 weeks but he always says how he loves me and stuff but obvs I don’t feel the same yet, (we’re both 15).

He wants to meet me soon saying how he’s going to a load of stuff to me that I don’t wanna be done yet, as I’m not ready, Although he’s done everything already.

I don’t know how to tell him that I don’t wanna talk anymore as I feel like I’d be letting him down, because he is a really nice person but always talks about sex and I don’t like that about him.

What should I say ? xx