I Have a Crush On a Coworker

I have a co worker who I think has a crush on me, and I’ve started to like him too. He seems to be as shy as I am for the most part, but two days ago I think he was flirting with me. Most of our Interactions have been on our staff bus, where we both smile at each other shyly from a distance, and don’t end up talking, then we go our separate ways as we work in different buildings. Then, there was one day a couple of weeks ago where our paths crossed and he started talking to me. It was just small talk, and I could see that he was trying to look at my name on my security pass, then at the end he said “see you later darling”. A few days ago he was working in my building for a few hours, and I made an excuse to go over to where he was working, by going getting a drink of water. I said hello to him and he smiled back, and I saw him watching me as I started to walk away. An hour later I found a reason to go over and work where he was. Again, we just had bits of small talk, and he was joking around, making me laugh. He called me sweetheart at one point. Later on I asked him to pass me something, which he did and said “.... only because it’s you. I’d do anything for you Rebecca. You ask me to jump, and I’d say how high?” I also saw him looking at me again after when I walked away. I think he’s trying to flirt with me and make me laugh, but he’s so shy, so I don’t know if it is flirting or him just being nice.