Situationship at work: is he flirting?

Context: I met this guy last year when I joined the company I work for. We worked on a project via Teams but I could feel an insane chemistry. After we finish the project the office opens but we’re no longer working together (as in the same team).
I could still feel the chemistry between us but we never had a proper conversation. He’d always touch my shoulders and smile as a greeting but that’s pretty much it. Never a proper conversation.

At some point were attending a work event and he was there with his gf. I decide that as much as it makes me upset I should probably not pursue anything. He keeps flirting, liking all my Instagram posts, touching me at work and then ignoring me for a bit then being nice and warm again. This situation goes on and on for about 6 months.

Last week we attend another event with alcohol involved and he tells me that I’m very beautiful and that he appreciates me a lot. I asked him something like do you really think so and he replied something like yeah everyone does you are the most attractive woman around I just wanted to let you know but I’m a professional guy I didn’t mean to hit up on you.I told him that’s a good thing and I appreciate him for just giving me an honest compliment.

I’m so confused. He basically told me he doesn’t want to act on this but he confessed his attraction (which I could feel for miles away). We’re not friends so it’s not like we’ll keep talking but I can’t get this guy out of my mind for a year. I even dated someone and decided to stop because I felt unfair from my side because I was so attracted to this coworker. Meanwhile I never confessed this to my coworker.

What do you think? What would you do? I actually thought of trying to take things further but I have no idea how.