Dear ManagoFandango:

“heavy breathing, strong and fast heartbeat, dizziness and shaking” means that your body is preparing itself to fight or to run away from what you perceive to be Danger (the well  known fight or flight response to perceived danger).

This co-worker is a  guy you liked a few years ago,  a guy who suddenly stopped texting you, ending with you “feeling hurt and rejected“. I am guessing that the Danger you perceive when you see him at work is the feeling of hurt and rejection you felt back then.

You asked: “what should  I do to stop feeling like this?“- as a start, it may help you to express the hurt and rejection you felt a few years ago when he stopped texting you: you can express it privately in a journal, talk about it to a counselor, or you can express it here, on your thread. If you do, I will read and reply to you further.

anita