Idk what's wrong with me

Now I am very much in love with my bf I would die without him he's the one I wanna be with forever. But... there's a guy at work who flirts and texts me who I'm friends with and I consider cheating. I've NEVER been one to cheat and I know that I never could go thru with it but I think about it all the time. My sex life with my bf is a little on the boring side but its ok with me bc my emotional connection with him is so strong. Why do I think about another guy when I am so crazy about mine. My life is finally drama free think maybe I talk to my friend bc I need excitement? My relationship really doesn't have any.... idk how to leave this guy be and just be happy