You put the knife to your wrist and learned something important -- you still think life is worth living.
I've done the same, but in different ways not a knife, but a knife-like ridge on a high mountain, looking down at the void to the left and right, or on the sharp end of a climbing rope, 20 feet, 30 feet, who knows how far above my last reliable piece of protection, and realizing that I don't want to die, I really want to live, no matter the hell I was going through the previous day or week.
I've thought the same about being a second-rate woman or not a woman at all, my confidence crumpling like a house of cards. And then there are times like a few days ago when I got in a (very) minor accident, and the guy in the other car had trouble accepting that male legal name, despite my not-very-feminine-at-all voice, getting very flustered. And then a waiter asks me if he can get me something to drink, "sir." It's hard, but there's progress. After some time, I have enough data points to see the trend toward being accepted as a woman.
You are 20. Hormones probably will do wonders. You can have surgury, and your face will be beautiful, of feminine at the very least. You won't ever be Gisele Bündchen. Nor will I, nor will any woman I've ever met. But if it's what you want, if it's what you need, you can progress and see changes, however painfully slow, and you'll have years of life as a woman, completely normal to every one you see.