Mindy.... you are in a great position here as there has been no BD and your H seems to still care what you think. However, you are running the risk of making him feel like your misbehaving child as opposed to your H. Please take others advice and back right off. This is NOT about her. If things between you and your H were really good, there would be no space for her. You need to do a 180 here if you want to work things out with him. Stop trying to control him...he will run for sure.
Consider your part in all of this. You are not in any way to blame but you have contributed. It is only natural that long term relationships start to get stale and people start taking each other for granted. This OW does not sound like a long term problem to me but she will become that if you focus on her. Instead, focus on you and what you can do to better yourself and remind your H of why he fell in love with you in the first place. GAL and do your 180s. Reconnect with the person you used to be when the two of you met. Pay attention to the things he is doing right, not doing wrong. I know this feels unfair and it is. But you need to ask yourself... do you want to be right or do you want to fix your marriage?
What Steve said... become AWOAFWL. Show him you will be just fine no matter what he does... and you will be if you do this. (((HUGS)))