Is he just being friendly or is there something more?

There's a guy at work who's shy and selective in choosing his friends. We've worked together and talked for 9 months, when I realized I'm starting to like him. He gave me his number for work purposes, but then we started to text each other almost every day. We would also talk after work when we finish late and no one else is around (longest time: 1 hour in the lobby just chatting...)

However, it always seems like I'm starting the conversations (IM, Text...) I'm more outgoing I guess and he's more introverted? (he's not a fan of social media so no FB account to do some research)

He's a co-worker and I have rules against dating co-workers, but I don't think I've liked anyone this much for a while. I just don't know if he feels the same way. I wouldn't want to risk our friendship or it becoming office gossip (or embarrassment).