Welcome to MB...sorry to read you are here.
IMO, you need to make a choice right now, right here.
Do you want to "save" your marriage? Or do you wish your marriage to end?
I would bet that if you are here on MB, you wish to save your marriage.
Your WH is escaping. Whether at EA or PA or a EAPA, possibly the tension/stress of now providing for you and his new family may be too much. This in NO WAY excuses him for having a female "friend" or to engage in any intimate contact outside his marriage.
At this point I would hold my "savage" tongue. Have all my ducks in a row and then ask to have a sit down with him.
In a calm manner (and may the Holy Spirit guide you at this time), let him know of your feelings. Let him know how this has hurt you. Let him know that you feel your marriage is in great jeapordy. Ask for him to attend a MC session, just to get you back on track, offer some skills to better communication.
Start going online and copying information IE: expedia.com. Plan the trip. Let him accidently see the information. This will put the "scare" in him that you might show up (and if there is ANY POSSIBLE WAY, show up). Tell him that you are going to try to find a way to meet him on his trip. Tell him that you think you should really go on this trip with him as a getaway just the "two" of you. Let him know how much you love him, because down deep you do.
I used to think "fight fire with fire", but I think it's best to "fight fire with water" or better yet, by suffication of a blanket of love. Right now I would look at your WH as a drug addict. He's sick and needs your help. Breathe and be patient.
If all your efforts fail, at least you've given it your best.
I will keep you in my prayers.
Peace,
holiday