Here's something I wrote on Twitter earlier this week:
"Pretty sure I'm the most jealous person who ever lived. I should be in that Guinness Book."
So yes, I can relate a bit.

I lost my teens AND most of my twenties (I'm 28 and just starting my transition). College was a nightmare. Being surrounded by happy grinning girls everywhere I went slowly drove me crazy. I eventually had a breakdown and stopped leaving my dorm room because I couldn't stand to look at them anymore, and wound up flunking a few classes. Bad times.
I know other people had/have it worse than me, but that doesn't make my jealousy go away, it just makes me feel empathy and/or sympathy for the people who are worse off.
I have been feeling better lately, though, largely because I've been writing comedy based on my experiences. If I can turn my pain into something that brings people happiness, then I feel like I didn't suffer for nothing. So that's how I'm dealing with it, and it's working for me more and more. Hope you can figure out something that works for you too!
Good luck with your transition, Rae. And speaking as someone who's seen LOTS of twenty-something girls having fun, let me just say: you can look forward to some fun times as a twenty-something girl.

Anna