can a nb person be afab and later realized that they were nb all along?

yep! that was how I was actually. I didn’t have any problems with being a girl before i found out about NB. but after i found out, it was like: “oh! this actually fits really well! and i’m not sure i actually like being a girl after all”

do you have to have dysphoria to be nb?

No. the only that matters imo, is gender euphoria. if you feel happy and content with being nb but you don’t feel discomfort about being your agab, then you are valid

what does it mean if your gender expression is sometimes like a girl and sometimes like a boy? (and you sometimes experience dysphoria). does that make you bigender or just someone who’s gender non-conforming? cause for me, I am afab, but I wouldn’t mind if someone called me he or she. I like both pronouns and i really want top surgery one day or at least a binder. (sorry if this was confusing) 🙈

I don’t know for sure, as when it comes down to that level of detail it’s best just to choose what label you think is best for yourself. You don’t have to pick the ‘100% correct’ label, you can choose whatever feels best.