Guy Advise - liking someone at work

So, I like this guy at work.

He definitely showed interest in showing me he liked me this morning by looking at my lips and eyes up and down this morning at work.

Afterwards, I was shocked 🥰😍.

I was surprised by it because I was unsure if he did like me, so I broke eye contact every now and again and held it because I wasn’t expecting it and we where talking about work...😩.

I did keep the conversation going though and maintained my body language (I was facing him when he spoke to me, when he moved I faced him).

I don’t think he realised we was doing it.

We walked passed each other a couple of hours later (in the office) and gave me a smile with no teeth showing, I smiled back.

He’s from Manchester in England, been living in London for 2 years and not to my knowledge has a girlfriend... I haven’t had the balls to ask... he’s been very open about talking about himself and his family\life.

I don’t know what to do next, I’ve felt for a while that I always initiated conversations with him and remember more about him and his weekends and the things he’s said.

Maybe I’m far more interested in him on a personal level instead of him being interested in physical attraction.

I feel somethings has changed from this morning though. We’re working on a project and he’s showing me some stuff together (only the two of us). Maybe I can ask about his private life when it’s quiet..

I would like get to know him on a romantic manner but not as some piece while he’s living in London board and not getting laid...

Please give me your opinions..

Also, I added him on Facebook and he hasn’t accepted me as a ‘friend’. Again, maybe I should just speak to him about it?

Thank you 🙏.