Liking a guy in a relationship

I work with a really attractive guy and the past few weeks we have been having deep, really good conversations almost everyday we work together. I don’t connect instantly with people but with him I have. We both just find it very easy to open up to each other I have caught feelings for him. I had begun to noticed what I perceived as flirtatious comments that he would say to me and him always wanting to talk and start conversations. I started to think he likes me too. However, when I looked him up on Instagram I was shocked to see that he has a girlfriend. Now I feel stuck in such a hard place because of the feelings I have toward him and the fact that he is in a relationship. Also, should I be concerned that he always wants to talk to me a start conversation? I am a teenager and not very experienced in these types of situations.