What's his deal?

Ok so I’ll keep this as short as possible.. Let’s call him J.
I’ve known J through friends for a few years and he lives in the same area as me.
Last year he began working in the same building as me, so I’d see him most days and began to get to know him a little better. Anyway, about 4 weeks ago I was on a night out with my friends (also his friends) and he was there… Long story short, he kissed me and he was a total gent the whole night. I knew that I’d see J at work the next day, I didn’t know how that would go, but it was great, no awkwardness at all, only he hasn’t mentioned the kiss since.
We talk more now than before the kiss and he always tries to catch my eye, but nothing more than that happened.
Anyway I then thought he’s just not that interested and tried not to think too much about the situation UNTIL last weekend I was out again, bumped into J and he kissed me again a few times and we spent a lot of the night together. So that was it, I just presumed we were going somewhere, I was so happy. I was wrong, I’ve seen him almost every day since, and he hasn’t brought it up once, we just talk as normal. The most frustrating thing is that all his colleagues in his quarter know about me and what happened! He just won’t say anything TO me! Help! What’s he thinking? Is he shy? Or is he just using me and playing a game? It’s hard when he’s so genuine with me at work I just don’t know what to do because I really like him!