<human>: Throwaway because paranoia. 

I've never really been in this situation before.  About a month ago I met my new coworker, who we'll call Jack.  Jack and I hit it off instantly.  Same sense of humor, same taste, everything.  We basically flirt with each other all day and quickly became friends on various forms of social media.

A couple days later, I found out through a third party that he has a girlfriend.  They've been seeing each other for about five months and it doesn't seem that he's as invested as her, but it's still pretty wrong.  The third party also let me know that this crush is definitely mutual.  I feel horrible.  By the time I found out, we'd already been facebook messaging back and forth for a bit.  Everything was innocent, and nothing has occurred that would really count as him cheating.  Even still, if I were his girlfriend, I'd be furious.

I'm caught where I want to distance myself from him and be around him all at the same time.  There's only so much avoidance I can do since will will see each other at work.  I guess I'm just looking for advice on how to navigate.  I in no way want to be a homewrecker, despite what my feelings may be.  Any suggestions would be appreciated.  I'd love to just be friends as well, but don't have any clue how to get over the heap of sexual tension.

Can you succinctly summarize the text in 1-3 sentences?
<bot>: I've been flirting with my coworker who has a girlfriend, which I only just found out.  Looking for advice on how to navigate from here on out.