It is possible? Sure. I'm reminded of the eloquent statement on love: It takes a minute to like someone, an hour to love someone, and a lifetime to forget them.
I might have that wrong, but the point is that somebody went out of their way to come up with a saying about how easily you can fall in love with somebody so it must be true. The better question is, how LIKELY is it that dude really loves you? And to that end, probably not very. He may think he's in love with you, but he's in love with the idea of being in love with the things he knows about you thus far. Of course, that assumes you all aren't spending every minute of every hour (possible) with one another as well.
Some people meet on a Monday and are married by Friday and remain that way for the next fifty years. Anything is possible when it comes to love and feelings. I don't discount anything. I do think that it can take a while to really truly get to know somebody to know if you really love them, unconditionally, like real love is supposed to be based on. But I do think its possible to realize that you're in love with somebody rather quickly. Heck since I wrote this, I fell in love with you and I don't even know you at all. Not even a little bit.
Ooops, there it went. That was fleeting. But for those few moments, what we had was real, girl.
What you might want to do is just let your guy know that you're not quite there yet but its possible for you to get there assuming he isn't creepy or pressing the issue - which he kind of did by telling you he loved you so quickly.
Um, viva la love.