Hi there. How can I say this politely? What the heck are you doing???
You need to immediately cut off contact that is outside of your husband and if you do see him . . . do NOT be flirty, do not look at him, etc.
It would never work. You'd be nothing but a conquest and a fling for him. Remember that always. 98 percent of the time, things like this end in disaster and that is taking out the element that this is your husband's friend. That makes it even worse.
You sound bored and I'd almost have guessed you were very young and not married by the way you describe this situation.
So, again . . . this may not be the polite way to say this but "get your act together woman". This is silliness and really cruel to do to your husband. Lack of character haunts you your entire life so develop your inner strength and character and focus on your marriage. good luck
I'd say that the attraction to the other guy is means all is not well at home, no matter how studly your present man is. It's never a good idea to leave one relationship for another, though. It makes the new guy think you are going to do it to him sooner or later, and besides, if you are not happy in the old relationship you should simply call it a loss and stop, without waiting until you have someone else warming up in the bullpen. It's like moral cowardice in a way, you need to stand by what you like and don't like even if there is no guarantee waiting.
In your shoes, I'd talk to a counselor with your present guy, and tell him that you are having some troubles with the way the relationship is going. Don't say he is not smart, funny or charming even if it is true (and you have someone else to compare it to), but fess up that you are beginning to feel uninspired, or that you want out, if it is true. And go out for its own sake, not because you're going to someone else.
If you'd been on your own for 6 months or more and had found your own feet and were sure of who you are, and then the charmer from your guy's workplace were to call, then have fun. But don't run from one to another, it's wrong on a whole lot of levels.
You're playing a very dangerous game and sooner or later you'll get caught. I strongly suggest that you quit the flirty kissy stuff with his friend and concentrate instead on fixing what's lacking in your relationship. If you don't cut out this flirtation with the other guy, I guarantee that you'll get caught and your life will be over. It's not worth it.