Welcome to SI. As mentioned earlier, it might help you to reframe what exactly your challenge is, and then you'll have a clearer path to resolving it. Take your username for example, it's actually a great example of what I'm talking about. Consider the average addict, let's say an alcoholic. If you were to ask them, they would probably say they are an addict because they have a problem with alcohol. But that's not really the truth. Many addicts, when trying to "quit", will instead just switch to a new addiction. They might switch to drugs, or smoking, or overeating, gambling, or even become workaholics or exercise too much. My point being, the problem isn't that they are addicted to alcohol, the problem is that they need something in their lives to help them to minimize or avoid the pain and stress of the trauma in their lives.
Many of us here have found that same approach helped us to recover. The problem isn't that we can't "keep it in our pants". The problem is that we have a hole in our hearts that we need to fill. Many of us have come to the realization that what we really were looking for wasn't sex... we had that already, being married and all. We were looking to feel special. We wanted other people to tell us that we're wonderful people, that they've been thinking about us, or wanting us, or commiserating with our struggles, whatever. In other words, the infidelity was a result, or a side effect, of a much larger, deeper issue. A person who loves themselves, who respects themselves and others, who has healthy boundaries, morals, ideals, and who doesn't need others to define their own self-worth, is someone who would NEVER have an affair in the first place. They don't need to, and even if they thought they did, they would never allow themselves to be that person. For example, if someone offered to pay you to kill another person, would you do it? I assume not. But why? What if I told you that you could 100% get away with it, would you do it then? For most of us, we would not. Because we're not murderers, and we don't want to be murderers, and could not live with ourselves knowing we had taken the life of another for selfish purposes.
Not having an affair is very much the same. The idea isn't to "white knuckle it", you've seen how that approach works for things like dieting and quitting smoking... it's a temporary fix that always fails over time. Rather, what you need to do is to remove whatever it is that is causing you to desire the affair in the first place. If there is no need or desire to have an affair, then there is no need to white-knuckle anything.
There are no quick fixes. There is no "do this and it will all be better tomorrow". And most of all, there are no guarantees. You need to do the work to figure out who you are and what drives you to cheat, and that takes a lot of introspection and self-reflection. It also takes enormous amounts of courage, patience, humility, and a willingness to look in the mirror and see what's really there rather than who we want to see. Most of all, it takes dedication. This is not an easy road, but I can promise you this much... it is SO WORTH doing.
Don't fool yourself. Not being in a monogamous relationship won't fix shit. Because the relationship isn't the problem, the problem is inside of you. Until you change, then wherever you go... there you are. You aren't safe to be in a relationship with, whether it's marriage, dating, friendship or work. As long as you allow your drive to seek out comfort and attention from others to be a priority in your life, you will always end up hurting yourself and others. It's a shitty way to live, a shitty way to feel, and a shitty outcome in life.
On the other hand... you have the power to change. And things can change quicker than you think, it's all really a matter of how open-minded you are, how honest you are with yourself, and how willing you are to "do the work" to change and improve.
We can help guide and support you in this journey, but it will still be on you to do the work, feel the feelings, and struggle with the struggles.
Start by looking at the link at the top of this page called "The healing library". It's a great place to start learning about what both the BS and WS go through. Take some time to read the articles there and start getting an idea of how your actions impact yourself and others. Then keep coming back. Don't be afraid to ask stupid questions, and by all means, be open to getting some "2x4's" (tough love) without running for the hills. We're going to say some stuff that might piss you off at first. That's okay, we've ALL been there. You'll survive. And over time, it will start to make sense and you will see progress.
Welcome to SI. Sorry to see you here, but you found the right place.