Sorry, this is going to be long, but I just need somewhere to vent.

My wife (42F) and I (41M) have been married for over 20 years. We married young, and for the majority of our relationship, due to both mental and physical struggles, my wife was relatively uninterested in sex. It was somewhat regular early on (1-2x's a week), and then by our fifth year it had dropped to once or twice a month. I come from a "never quit" family that demonized divorce, so that was never even discussed. And to be honest, we do get along really well, hardly ever argue, enjoy each other's company. But, for almost 15 years, I sat up until all hours of the night while she was struggling with panic attacks, talked her down when she was borderline manic, taken care of the kids when she could barely take care of herself and certainly not them, fended off verbal attacks when she was sure I had looked at some other girl "that way", wrestled with also not watching porn and not masturbating because that made her "feel bad". And through it all I stayed, in part because of the kids, and in part because I wanted to see her get better and "that's what good husbands do". I spent hundreds, or maybe even thousands of dollars on sex toys and lingerie and swings and pillows and chairs, etc. trying to spark her interest in sex. But for the majority of that time, we would go weeks, often months without having sex. I even got to the point where I stopped initiating because I got tired of getting turned down. A few years ago things started to improve. She received several diagnosis that explained a lot of the physical and mental issues, got some medication and started going to therapy. Things were good for about 10-12 months. Honestly, at that point we had been down that road for so long, that we didn't even see that our sex life had been a problem before, so now, 10 months of having sex every week was like utopia. Through some long conversation, we decided to explore swinging (I know, I know. But things seemed really good, and we never really identified that we had a problem before). Honestly, I had hoped that it would help unlock some of her sexuality. However, we have never been able to find a couple that was interested in both of us, so it's become just my wife hooking up with other guys. At first I would go along. It was super hot and made my wife hornier than she's ever been. She was insatiable, even at home. We were having sex once or twice a day, she was sending me nudes while I was at work. She even said that she wanted to try a "challenge" to have sex every single day for 30 days straight (which would have been a first in our marriage). That lasted 16 days... Slowly (or quickly, I suppose), things at home faded. Due to kids and work schedules, I was no longer able to go with her when she was meeting with other guys, and when she came home, she would be "too tired" and "too sore" for sex. Eventually it got to the point where she was having sex with other people more often than she was with me. Finally, we sat down and had a long conversation about where we're at. A lot of things were said, but in the end, she told me that my penis is too small for her to enjoy having sex with me (on the smaller end of average). So, between that, and having teens in the house, she feels like our sex life is mediocre and she doesn't enjoy it. And by her own admission, she never thinks about our sex life or having sex with me, she just simply enjoys having sex with other people more, even though she "feels bad about it". She's even encouraged me to try to find other women to have sex with, so that she doesn't have to feel bad about meeting with other guys (my own wife doesn't want to have sex with me. Not a ringing endorsement when trying to find another woman). So, over the last 15 years, I've purchased every single sex toy, every piece of lingerie my wife owns, to help her tap her sexy side, paid for laser hair removal and braces and skin creams to help her feel better about herself, with absolutely no contribution on her part...until she started meeting with other guys. Now she buys lingerie before they meet up, is starting to pick out some of her own sex toys. The result? I'm sitting at home, haven't had sex in about two weeks, and she's on a weekend sex retreat with one of her guy friends. In fact, the last time we had sex was two weeks ago, when she convinced me to have a threesome with her and her FWB. Honestly, it was pretty amazing, but we haven't had sex since. But, the thing is, she seems to be under the impression that things are all good. She has commented that things are "good with us" and references our threesome. She doesn't even seem to recognize how it feels when she says that she "actually" enjoyed having sex with me during our threesome because she could "actually feel it that time". Or when she mentioned that last time they were together for an overnight she and her FWB, fucked twice and she gave him a BJ four times. She even commented that it was "her fault because she's so sexually aggressive", and when I noted that it was more sex than we typically have in a month, she just laughed, then acted hurt. Didn't change anything. I'm definitely getting screwed, just wish it wasn't by life.