Most Helpful Guy
It seems as if he's not interested. If a guy says he'll call and then doesn't, that's usually a fairly good indicator he's just not into you. Of course, there's the chance he's a shy guy and has problems talking to girls.
Because he's possibly going to be your first, you might be putting a lot more importance into him than he deserves. From an objective point of view based on how you say he acts, I'd say he's moved on from January when he said he liked you.
The reason I'm putting it all this way is to keep you from getting your hopes up. I'm not saying you shouldn't pursue things. I'm just saying be prepared.
When a man takes a woman's virginity, he feels highly responsible for her entry into the sexual world. If he's heard that you are a virgin, he'd probably have some fear and trepidation when you flirt with him, especially if you tell him you like him. If you and he start a relationship, you should let him know fairly quickly that you're a virgin, if you haven't already.
So, it's a mixed bag of advice this time. There's a lot to process. I don't generally recommend love affairs in the office. When I found out you were a virgin, though, I had to encourage you. I don't know him and can't say if he's still interested or not. I can say that if you don't let him know somehow, you'll probably regret it.
Go for it and take a level headed approach to things. Take office politics into consideration. Is your workplace a gossip mill? If so, I'd find another guy outside of work. Doesn't matter how it turns out, this is juicy.