Guy problems??

ok so there's this guy i've known a month or so, and i'm not normally the type to fall in love quickly but we were infatuated from the start, anyway the other day we were exchanging soppy texts and he said he thought he was falling in love with me, and at the time i felt a strong emotional connection to him and believed myself to be falling in love too. we've just started getting physical although haven't had yet, but by the sound of it he is convinced that we are going to have a serious relationship..i though so too at the time but everytime we meet up we are really stuck for things to say and this makes me think that it's more lust than anything else despite how sweet he is to me..anyway how do i let him down gently..i'm still attracted to him but don't want a serious relationship atm?? btw, i'm 19 and he's 18