Hello, FullofConfusion. Welcome to SI from a fellow WW.
The first step in finding remorse -- and it's a tough one -- is to stop using the word "but." To quote Game of Thrones, "Everything before the word 'but' is horseshit." We waywards love the word "but." "I know I was wrong, but." It makes the "I know I was wrong" sound like horseshit, because it implies that cheating was in some way justified because of the life circumstances of the cheater. I don't mean that your complaints aren't legitimate grievances in the marriage. What you describe sounds terribly stressful, and it may have justified counseling or separation or divorce. It's just not a mitigating factor for infidelity.
Unfortunately, an offense like cheating deprioritizes most other issues in a marriage for a very long time. If your BH wasn't willing to hear your concerns before you hooked up with your AP, he's unlikely to give those concerns much time or credit now. He may file for divorce as soon as you tell him about your affair. Or he may spend a few years trying to heal and realize that he can't stay married to a woman who betrayed him. Or he may use the A as an excuse to punish you at every opportunity. Meanwhile, those other marital problems won't go away. It's very rare that a BS becomes more receptive or understanding in the aftermath of betrayal. Why should they? Frankly, it wouldn't be healthy for them to do so. The "pick me dance" is an act of shock and fear that doesn't promote true healing.
By now, you're probably thinking, "Gee, thanks, BraveSirRobin. I already knew I fucked up, I already knew I was in deep trouble, and that's why I came here for help. Why would you, a WW, kick me when I'm down? Don't you remember what this was like?"
I do, and that's why I'm saying all this. In the wild phase immediately after betrayal, you are desperate for expedited ways to fix it. To make it unhappen. The same brain that got you into this mess will tell you a thousand lies about how to get out of it. It will tell you that you just have to make your BH understand. "I never would have cheated if I hadn't felt so miserable and unheard. This isn't who I am. I'll never do it again, and I'm so sorry, and can't we please let the past be in the past?"
But this is who you are. Something in you gave yourself permission to cheat, and that capability was unsuspected both by you and by your husband. It's gaslighting to pretend otherwise. He has no reason to believe you will be honest about everything that happened, or that you won't do it again, or that you have never done it before. He can't read your mind. In the best of circumstances, where you confess openly and hide nothing, his entire sense of reality will still be kicked out from under him. It's exponentially bigger than your own panic and disbelief, because you saw the affair developing and made the choice not to stop it. He did not.
Your cheating completely changed the dynamic of your marital problems. Metaphorically, you brought a gun to a fist fight. Your bruises will now need to be triaged while he's bleeding out from a gut wound. You'll need a lot of patience and therapy to develop healthy coping mechanisms as opposed to unhealthy conflict avoidance. It will be a long time, possibly years, before you're independently healed enough to start healing the marriage together.
So here's a question, and I ask it sincerely. Are you sure you want to go for it? Do you have it in you to tolerate not only the pre-existing circumstances of your marriage, but to live with a furious, desperate BS who doesn't trust a word you say? With a stepdaughter who may see the advantage of you being in the one-down? Are you prepared to be honest and supportive even if he's aggressive and dismissive? Because if not, divorce might be the best option. You have to really, really want your marriage in order to do what it takes to have a chance at reconciliation, and even then, it's just a chance. There are no guarantees.
I don't mean you should run away from your problems. You have to face your BH with the full truth -- you owe him that for his own healing -- and you have to get to work on yourself. Even if you decide to end the marriage, you can't be a safe, healthy person in your own life without exploring why you allowed yourself to turn resentments into justifications. That's your internal work, though. If you believe that you can approach this as a "fault on both sides" negotiation, your chances of success are very, very low.
I haven't been around for a few months because my BH and I felt like time away would be good for us (and it has been). The only downside has been my concern about a lack of experienced wayward presence on the site. I can try to help, because I've been there. But it wouldn't be fair to you to pretend: it's likely the hardest thing you'll ever have to do.