Situation with a co worker

I’ve been into this girl I work with for a few months but never did anything about it because she has a boyfriend of 5 years. I always thought she was into me too but wasn’t sure.

One month ago she broke up with him and in the following week during a night out we talked for a good amount of the night and she kissed me.

Two weeks later she got back with her boyfriend. I really like her so now I’m keeping my distance at work. I think it’s safe to say I have feelings for her. So any personal interaction with her kind of hurts. But she’s been asking me whats up with me non stop, and is trying to figure out why I’m so distant and don’t talk to her the same as I used to.

I’ve just been answering vaguely and playfully but it’s getting heavy. What should I do?