The question of being "trans enough" or "nb enough" or "gnc enough" etc. is a widespread doubt, and I'm sorry that this has been stressing you out for some time, alongside the horrible misgendering you've been confronting. First: yes, you are absolutely agender enough, simply because agender is how you see yourself, because it's an identity that you find comfortable, and because it is what you wish to be seen as by others. These
will definitely bring you some comfort and reassurance.
As for everyone feeling like a "person" deep down inside, rather than their gender: I wouldn't be so sure that this is universally the case. For many people (both queer and cis), their gender identity may be essential to how they view their personhood and their selves. The fact that you don't count gender as one of the essential facets of your inner self is all the indication you need that you're fully agender. Embrace it!
Second, gender and sexuality markers are not meant to be earned, they're meant to make you feel comfortable both in your own person and out in public. They're also meant meant to help you explain personal traits, preferences, and experiences that you find don't fit the cishet mold. So there's absolutely nothing to feel guilty about regarding your being agender. No authority is going to come up to you and confer the agender identity upon you as a recognition of your suffering, or whatever. You are that authority for yourself, and you don't need to climb a couple mountains before you feel worthy of being agender.
Sorry I didn't answer whether or not I've felt the same way as you do right now, but I'm sure some of our other users will share their experiences!