Crushing on my colleague

He knows I am married and he also has a girl that he’s currently chasing. He is helpful, friendly and humorous. I feel attracted to him because he’s tall and strong. I can’t help but feel flutters when he gets near me. Is this normal? I take the same bus with him everyday after work since we only live a few blocks away. My husband also know him and even jokes to my son that I have a new boyfriend. Ahhh what should I do? Difficult to avoid him unless one of us quits….