Frankly, I don't think not telling your lover about stuff from your past that isn't directly relevant is normally a big deal. Just because you love someone does not mean they have either a right or a responsibility to know every single thing about you. There's stuff that is nobody's business. Communication is important . . . if it's about stuff happening now, or at least stuff that's going to have an impact. If it's some "dark painful past" thing, then maybe you'll tell them sometime and maybe you'll just leave it forgotten, but not telling them shouldn't be a relationship-breaker IMO.
Admittedly, "all of middle school" when you're only in your 20s and people from middle school may still crop up from time to time seems like kind of a big chunk to sweep under the rug. "Prince" huh? I'm wondering if, when she hit middle school, liking girls and looking boyish, she ended up adopting some kind of elegant prince stereotype persona which was so different from what she's actually like that it ended up making her barf.