BOYFRIEND IS TALKING ABOUT HAVING SEX WHAT TO SAY?

[Alicia]

My bf and I are both 14 (well i am 13 and a half)and been together for 2 years but, the other day and I was hang out with him at the park . When he said ''so when are we going to do it'' and I said ''do what'' and he said ''sex''. At that time i didn't no what to say so i started laughing . Then he said i am for real so i told him we will talk about it tomrrow and walked home. But the truth is I didnt no what to say . What do u think I should tell him i mean i known i can say no but couldnt why. thxsbot