Stop guaranteeing security in your commitment , if they want to keep you around make them convince you of that every day. It’s this premise that you might not call your partner tomorrow for a second date that makes them crave you.
Stop spending all the time together. In fact take whole days apart either in terms of attention, time, and/or space. Learn to miss each other in order to remember that love is not always a given, and as such desire should return because as renown psychotherapist Esther Perel points out � love is to have, desire is to want. You can’t want what you know for sure that you have.
You need to find a woman who remains sexual for a long time even without marriage and if they change, then weigh up your odds on staying and leaving, but sadly you will never marry someone and have them stay that way forever
Start acting and behaving as you were before you moved in, married, or as I say reached the �pinnacle of love’. Take this example. You go on a date, they show no interest whatsoever in terms of desire � for whatever reason � would you go on to show them love. No. Why is it that you would go on to do this now? Because you are putting your partner on a pedestal. Your partner finishes work, you begin to kiss them, they tell you they are too tired for intimacy. Why is it that you are pushed back day after day when before you reached the �pinnacle’, nothing was ever enough to stop them from tearing your clothes off and showing desire. It’s because you are being taken for granted, at least your love. Your partner can’t crave your love if all you do is give it to them regardless of anything.
Fmwsom
So. I wanted to add my 2c here. I’ve been looking into this topic for years. Books, forums, therapy, sexual therapy. I’ve done it all. Maybe 10 years.
Like many our issues started after kids. I was de prioritized, maybe rightfully so, but from then on I just couldn’t get myself to appear appealing to my wife. Everywhere I went, I 
read the issue is my fault. I don’t do enough, I’m not romantic enough, I don’t clean enough, I’m not fit enough, then you’ve got the other end of the spectrum. I’m doing too much, I’m enabling, I’m encouraging, if I do everything and she is rewarded with a loyal lapdog why should she ever change. I found the redpill ideology and I nearly fell for it. It’s the man’s job to take charge, be fun, entertaining, be fit, make bank… Everything. EVERYTHING I found was always on me.
The truth is, despite making great money, having a six pack and big arms, walking the fine line between doing my part, and enabling, between being flirty and overtly sexual, between doing things for her and doing them for myself, the issue was never about me. You have to find someone who wants sex because they want it, not because you did a song and dance and successfully juggled them into excitement, but because they have a naturally high libido, or at least are interested in sex. Do they read about it, do they have it even when they’re tired. Do they masturbate? If they think about it without you, then they’ll think about it with you as long as you don’t let yourself go, you don’t have to be the hulk, as long as you’re not depressive, you don’t have to be an entertainer.
The whole problem with this is people present an image when they’re first dating of something their not in order to lure you in. My only real advice is to be honest with yourself about your role, but hold her accountable for her role as well. If she changed the status quo and is refusing to accept that, then you need to leave. You have to leave even with kids because you need to show them that it’s okay for relationships to run their course and that your happiness is equal in value to hers. People change. You just have to evaluate and move on and be grateful for the time you spent even though you’re no longer compatible. That said from a marriage side of things, I would never get married. Why on earth would you get married when one party can unilaterally change one fundamental aspect of a relationship on a whim, then if you try to leave to find something more suitable, you can be financially crippled for so long, you may never recover. Don’t marry. Don’t marry. Don’t marry!