Will the loneliness dissipate?

mrslowmaintenance, I too am married to someone who I genuinely love and adore. Our marriage is actually very very good in so many ways but I too got to a similar point as you. The lowest was 8 times in a year and 10 times a year was about the norm. How did I know that it was this because I too started tracking and marking my calendar. And finally, on a night just 8 days after we'd last had sex, a night where wifey and I had been in together all day and night she went to bed slightly earlier then me and I too went upstairs and caught her jerking off. She had gone to bed "tired" yet I caught her nearly 90 mins later when I was in the way up. She didn't realise she'd been busted either and I kept it from her. I started to check her phone internet history after that for around 6 months and I found that she watched porn a couple of times each month. The fist occasion I caught her she definitely wasn't watching porn so it suddenly dawned on me that she jerks off with porn and without. Give or take I managed to uncover that she jerked off about once a week. I feel hurt, I felt undesirable, I felt cheated on, I wondered if there was a performance issue on my part (not that I have had any complaints from any woman including her and orgasms for her were always included in our sexual encounters). I literally felt like she had been having an affair from the beginning of our relationship and it absolutely devastated me. Worst of all though is with an affair you have the absolute right to divorce and everyone would understand. I had the dilemma of do I divorce someone who doesn't fuck me enough and who I've caught masturbating which feels like an affair? Anyway, I finally gave the game away to her and confronted her and I simply got told that she has a low libido, there is nothing wrong with how we have sex and in fact she "loved" what we did and that jerking off wasn't a sexual act to her. Our marriage started to decline for around a year because I became a refuser in other ways. Do I want to make the effort to spend time with and make room for this person who sneaks behind my back and has sex on her own? It got to a stage where we were close to splitting and we went to couples therapy. During those sessions we were told out right by the therapist that sex is important and you should try and have patience and understanding for your spouses sexual preferences as well as your own. I felt I'd been patient, understanding, in no way pushy and literally My wife had been pissing on my back and having sex whenever she pleased. The therapist said a compromise should be sought! Well I have to say things have improved for me and my marriage. Not much but 2016 saw us being a great couple again, spending time and as for sex we reached the dizzy heights of having sex 19 times. Why do I still visit this site because I suppose I am still getting over how badly this all affected me and it is a place to unload what's in your head or what's been in your head for years.Also I come here through fear that our old sex life is just around the corner. I truly hope not or it will be probably be affair city for me.
So you need to talk with your partner to see if improvements are possible because if you're anything like me, no improvement would definitely have led to me systematically dismantling of the marriage because being faithful in a marriage is so much more then simply not shagging other people.

You've pretty much hit on all your options in your one sentence.  To recap, you can:

1. have the necessary discussions with him so he can change is behavior... if not to change to fully what you want/need, then at least "meet in the middle".  This will take frank discussions, a willingness to change on his part, time, and quite likely some professional help.
2. "get used to it" -- lower your own desire and libido, and/or just lower your expectations and make do with low/no marital sex.  This might also take therapy: individual therapy for you!
3. stay in the marriage, but go outside the marriage for intimacy.  (not saying it is a great option for everyone... just sayin' it IS an option).  This takes time, some money, and a great deal of risk.
4. leave the marriage.  This takes a heart wrenching amount of work, and a boatload of money.

Sorry to tell you what you already know, but ALL of those are difficult.   The first is the most difficult, because it requires TWO folks to change... and if he doesn't want to change, it is off the table.

While you decide how to work on option 1, you have to get used to the idea that you MIGHT have to choose between options 2, 3, and 4.

Personally, I've tried 1, 2, and 3, each at different times and to different degrees of "success:... but none is a long term solution.  So I'm steeling my resolve -- starting to make life decisions -- for option 4.

I am censoring my thoughts right now. I really hope this works out for you.

I don't think I could leave. I have spent years helping him build his career, I am just now back in college to try and finish what I started ô years ago. We have a child, and retirement assets that I don't think I could truly recover from losing.

Or... Now this may sound awful... Is there something he can eat or take that may increase his desire??!! Lol, what a joke right lol

OK.
Rule out the porn as the "why" he is sexually uninterested in you.
Select another "why", say 'low T', and chase that one over the horizon and back.
When that proves a pointless pursuit, select another "why", and chase that one around and round.
Do that until the penny drops that it doesn't work.
Your mileage will vary on how long this realisation takes.

Then, revisit those 3 options you've got.
Stay - and keep "why" chasing.
Cheat.
Leave.

There is no 4th option whereby *you* can fix *him*.

If, there is "fixing" to be done, it will be done by him, of his own volition - his own choice - or - there will not be a fix.

You can't recover from it while you are still in it. If your situation changes then you have every chance of making a full recovery.

Can you get used to it? That might depend on what you mean. Lots of people live with it, but it eats away at you from the inside and it is always there. It is like being an artist and spending your whole life working in an insurance company, or growing up in Italy and then deciding to spend the rest of your life in a cold, grey rainy city where you never see the sun. Yes, you can do it. Will you feel you have lived your life to its full potential? Unlikely.

I know you have a lot invested here and there are lots of good things about your marriage. But please consider you are 26, and you have been in a SM for 4 years. Project forward another 4 years of the same and think how you will feel after 8. Then double that again and think how you will feel after 16 years of SM. At that point you still won't be 40 and will have another 30/40/50 years ahead of you. I am not saying you should necessarily leave. But you need to change something if you are to create a life that will make you truly happy.