djtanner Hi. You are not alone. There is a group here on SI for those of us whose partners/spouses betrayed in ways similar to yours--it's the EI-Emotionless Infidelity group in the ICR I Can Relate Forum.
There you will find many others who are dealing with what you are now. I learned 2.5 years ago that my H of 35 years had spent the past 10 visiting massage parlors twice weekly. You're "lucky" to have found out way sooner.
Like you I found out by seeing the cash withdrawals. Along with all other horrible emotions, thoughts, I felt really stupid. In all those many years I had never noticed the cash withdrawals. And then bingo, months before he was to retire . . .
So yes, you are in shock; learning this, finding out is traumatic. It is humiliating. It is disgusting. It is shocking.
Like your H, mine always did it work days. Never missed a beat at home. Like yours, mine said it was just about escaping from work. Then it became a habit.
So what to do? Be sure to be tested for STDs; be sure that he is tested too. He may say he had no intercourse and that is very possible. I believe mine did not. But testing is a must no matter. First we can't really "know" for sure what they did and second there are other ways to get disease. Less likely but possible so get that out off the way. It may even feel a bit of relief.
Find a good IC for yourself; someone who is experienced and well trained in betrayal trauma. Your H should be working with an IC as well. There are many ways for people to deal with stress. Our H's found a very unhealthy way. Their way violated us; their way violated our relationship. They need to examine themselves; they need to understand how demented, how damaging, how sick their choice was and they need to work to change.
There are several support groups that may help you regain balance. I regularly attend an SANON group and try as often as possible to attend a BAN group. These are marvelous IRL groups of people dealing with similar if not identical problems. It's great that you have found SI; it's been a life saver for me and for many, many others. SI is a great part of the team you will need to deal with your new life--the new reality.
Check out the resources from the Healing Library (upper right hand corner in Yellow box). There is much free and useful material.
You must tend to your basic health. Eating and sleeping properly is a must and can be very hard during this time. If you are not getting proper rest and nutrition then try mindfulness exercises, OTC sleep aids. if that doesn't work, speak with your PCP. We need all of our strength to deal with this.
It's highly recommended to try not to think about whether to stay or go; R or S or D. It's too much of a burden right now. Think about all to do to just work out of the stage of shock. Again, that is where a good IC can really help.
Your H should be ready and willing to answer all your questions and you may have the same ones over and over. We usually do. "What was wrong with me?" "why wasn't I enough? "How could you" "Why didn't you just leave?" and so on. Then there's the anger; the disgust. Anger over the betrayal--the money spent-the deception.
Ah, the deception, the double life. How weird, how sick. But again, you are not alone.
So please feel free to ask for any support here; check out the EI group. You will be ok. it will feel less crazy in time. You are not alone.