You need to think, "do I LOVE this married man?" If you do, think "Do I love him more than my husband?" This is very common for married people to have feelings for another man/woman. But in the end, you need to look back and see if your feelings for this man is deep, or if it's just a crush. If it's just a crush, remember that you love your husband, and that it's just a crush. If it's deep, well there's not a lot to do if he's married, and your married...unless an affair, which is a horrible, horrible thing to do.
You better figure it out sweetie or you will be single.
You need to tell yourself, that you are still a marry women.
Sleep with him. That will help you get over the feelings.
Focus on your husband! Don't cheat on your husband, and btw, I doubt the other guy would cheat on his wife. Good luck! <3