I think a lot can come down to perspective. You had a good time with your friend. Remembeer it for what it was and let the past flow behind you. Maybe when you hear him laugh, you can just appreciate what you two have had and try to let it go at that.
It is hard being physically close to someone you can no longer have a relationship with. But you can try to turn it positive by focusing on the fond memories and less on the breakup itself. Over time it gets easier to deal with it. So it is just an endurance contest in a sense.
So does your husband just assume you have a low sex drive or did you tell him that you are not sexually attracted to him? (It is pretty common when someone takes a lover, their overall libido increases.) How is he handling that?