Will my husband's feelings pass?

Only one thing to do. Go up to him very calmly. Act normal as if nothing was wrong and ask him CALMLY. Don't start crying or yelling. Just ask him if he loves her and if he has any intention of changing as if you were asking him what he wanted for dinner. Be calm. If he denies it then tell him you know and how. Good luck. I hope everything turns out ok.