"communication is weak, driven by her expectations from me. She's really dependent on me".

Dependent how? Financial, social?

Asks for help and gets upset if I'm not available. Explain, help with what?

Not a lot of info on here, but does this girl need you as an emotional tampon? and wallet?

Then, what do you want in a relationship?

does this girl meet those expectations?

write it down, see if she meets t hem or not.

I can see right now this isn't going to end well for you.

Yes, you are the problem. Your frame is all out of whack, and you just keep handing her the bullets she will eventually use to pull the trigger on you. You may have started as alpha, but you've become too beta in her eyes, thus the expectations of servitude, annoyance, arguments, and apologies. You're becoming so desperate to hang onto this you're even proposing marriage to try an keep her reigned in.

In the end it won't work.

You know you're fighting a lost cause, and you can't justify to yourself as to why you should be hanging on to this relationship, so you're reaching out here for validation and justification as to why you should keep going with it. Clearly, it's not in your best interest to be with this girl. You knew this a long time ago and tried to prove to yourself you could have other women, yet your scarcity mindset sent you back home with your tail between your legs.

It's never fun to watch all you worked for in a relationship go circling down the drain, especially after years and years, and it hurts like a motherfucker to let it go. Your mind is not right, and having gone through this myself, I can tell you the only way you're going to get back to normal is to break it off completely, disappear from her life, go sit in the corner and cry your eyes out, figure out what you did wrong, and start the healing process.

It really sucks, but you have to accept there's no salvaging this.

You have to do what's in YOUR best interest. It's not fair for you to keep torturing yourself. When you come out of the tunnel on the other side, you'll look back and think how much of an idiot you were being. Hopefully, you will have learned your lesson and will do better next time.

She knows how my affair made me realize how much I love her.

Unlikely that she believes this.

Our communication has been always been weakest driven by her expectations from me and my lack of acknowledgement. She often asks for help and gets upset if I'm unavailable. I feel like I'm expected to constantly serve her needs, leading to a cycle of annoyance, arguments, and apologies.

Right. She's insecure and annoying.

On her mind, Im not fulfilling the future husband's responsibilities. So not sure if not getting engaged after this long of relationship is also affecting her?

It is not your job to be a provider for her. She may want a slave, I mean husband...... this does NOT mean it's a good idea for you, a good deal for you. You are not obligated to be her future provider-slave.

. I'm unsure if this dynamic is typical in long-term relationships or if I'm the one at fault

It is typical, but it's also immoral and wrong. You are being shepherded into a life of slavery and service to an insecure girl who will never appreciate you for who you are. This will get worse, not better, the more commitment you show.

. I'm here seeking advice: am I the problem in our relationship?

your instincts are telling you that this is a terrible idea, then you blame yourself for not being what SHE wants.

How can we move forward from this? I want her to understand me which Im not sure if that will happen

Can't happen. She is driven by her emotions and her biology, you cannot change this and neither can she. She will always push for commitment and resources from you (legally mandated of course). She will always be insecure and demanding. Marry her and you'll be in a world of hell, the only thing maintaining her good behaviour right now is trying to sucker you into marriage.

Good luck.

Relationships are at their best for 3-5 years max.

You have a scarcity mentality, oneitis really. You are looking at it as a secure future prospect, rather than the more realistic "how much mileage can I get out of this?"

The truth is probably that your current relationship dynamic is the only possible dynamic for this relationship, and it will (most probably) disintegrate if you try to force some other dynamic on it.

How old is she? I'm assuming same age, so she's reaching the point where her biological clock is ticking towards getting pregnant ASAP otherwise risk high risk pregnancy, along with other social pressures like her friends & peers getting married and her seeing that shit on social media dictating her feelings and behavior towards marriage.

If you feel she's pressuring you to marry, then you'll only grow resentment in the relationship if you do something outside of your own volition, which will lead to either: you stepping out out of self respect; or staying in and losing self respect while you rationalize your sacrifice. Self sacrifice in this regard is the wrong move IMO.

Make her get upset, let her feel bad. YOU DO YOU. You're the man on a mission. You are the prize, and model type girls like you too and she knows that, so she will bend to your frame as you are the leader.

You genuinely hold the keys in this power dynamic but I sense a part of you that is highly empathetic so you won't go full on dark triad Machiavellian on this shit, which means you will have to have some level of compromise in order to continue the relationship.

I suggest you spend time with yourself and introspect on what you really want, and what you're willing to give up. Women will say things based on their feelings, but will still stay with you despite things not going her way because you're just a top option. However, even the biggest and baddest chads will get left if you never decide to commit.

The choice is in your hands.