I know some consider me at risk for a RA. I know I've thought about it myself. But it's only a passing thought. I absolutely WILL NOT do it. If it were going to happen, it would've happened by now, probably with that girl in my OP. It was right there for the taking, I could have gotten laid by an attractive girl 11 years younger than me without exerting any effort at all. She probably would've been willing to do things my wife USED to do, but would never do now. I might have actually gotten to experience good sex with an enthusiastic, passionate partner who wanted to be in it with me. But I didn't. I turned that down, I'm proud to say. It was never really a serious option for me. At the end of the day, my moral compass would never let me do that. I just know the damage infidelity can do, and I will NEVER be that person.
If I were your wife I think I would want you to say what you said in this paragraph. It is honest, it explains that you are not really looking for an affair, but that because that element is missing between you that sometimes the thought can creep up. Honesty is how things evolve. It's not a threat, you are saying you don't want to do that, but if she really loves you, I feel that she needs to evaluate whether there is more she can do to get back in touch with her sexuality. I might would even follow up the discussion with, "I am teachable, if what you need to get into it has changed, or if you want to explore more, I would be totally into getting that feedback from you".
I say that not to imply you aren't satisfying her, but from the lens of a wayward wife - If I wanted something different, providing critique or teaching my husband something *could* be intimidating, because:
a. You all didn't have sex for like a year after the A, so when it finally happened she likely wouldn't want to rock the boat.
b. It may be hard for her to be vulnerable and say "my shame is killing this" and honestly, if that's the case she needs to get back into IC.
c. She may understand that you have been wounded sexually and have fears that providing guidance to you on working on your sex life is out of bounds.
I don't know if I am articulating this correctly, but the thing I can't really understand about what you say in here is that she is in her mid-30's and literally never interested in having orgasms. You say she used to not be this way, so I don't think she has a frigid nature. Is there sexual abuse in the background? Do you have any hypothesis other than the shame around the sex?
You two need to open up to each other. I know that's scary on both sides. But, she really does need to understand by not being able to address what needs to be addressed here she continues to put your marriage in jeapoardy. Not because you are going to cheat, I don't think you are, but because your dissatisfaction is growing and growing.
It's not lack of sex. You say she is willing 2 or 3 times a week, which for most long term happily married couples I think is average to above average. It's lack of her showing you that she sees you as her love, her sweetheart, that she wants you romantically/sexually. You miss having intimacy. I can't help but think that the reason some of that is not there is emotional intimacy needs to be worked on.
Prior to my A, we had sex the number of times a week you are talking about. I was often interested in it, but it was missing that emotional intimacy piece of things. When we started having that piece over this past year, it fueled the whole thing differently for me.
So, maybe even ask her about that. I think there is a rich opportunity here to talk about how this situation reminds you of what you want with her. If she loves you and wants this marriage, I really think she needs to have a serious conversation about all of this with you and really take in what you say about it and be vulnerable enough with you to share back what the issue is. I personally think that she may need to see IC, or a doctor about hormone levels, or give you some feedback on what it would take to crave you. As a WW, I wonder if some of it is really an issue of emotional intimacy and what that would look like.
At the end of the day, two people who want to be happily married who are reasonably compatible with each other should both be interested in removing barriers to why that is not happening. Time to find out a. is she interested in removing the barriers? b. are you? and if so, c. What are they? You would be astounded to find what a little bit of work can do to reap a whole lot of reward.