For what it’s worth, you’re far from running out the clock. If you’re still in your 20s you have a lot of life left to live and are lucky you’ve figured this out as early as you have, even if it doesn’t seem like it.
I don’t know what you’ve already done, but one approach is to try less extreme measures first and ease into it a bit. Clothes, makeup, mannerisms, pronouns, etc. You could consider stopgap measures like focusing on hair loss prevention/restoration as a way to buy time and feel like you’re doing something concrete while you sort your feelings out.
Some of these themes also touch on topics discussed in this post from a while back - you may find some of the discussion helpful: lemmy.blahaj.zone/post/4266431
EDIT: Forgot to specify; these are definitely common feelings, if my own experience and internet-binging results are any indication. You’ll get through it. ❤️
EDIT2: lol, I didn’t see who posted this until now. 😅😭🤣