You rush over to the boy's bathroom, hoping to get one last moment of pleasure in you life. One last chance to feel those wonderful feelings, look at your dick while sitting on the toilet and think about how much pleasure it had caused you over the years, and soon it would be gone.
You start rubbing your dick, trying to distract yourself from the thoughts of impending castration. The fact that this was your last time being able to do this. You look at a picture of your girlfriend that she had sent you, she was so hot, her slender body, perfect breasts. Soon you wouldn't be able to do anything with her, you'll both be stuck without genitals after tonight.
Eventually you get yourself to climax, feeling the intense pleasure and then realizing it was gone forever from you. Now that you've came for the last time you'd never orgasm again.
You then make your way over to the room where they change your genitals. You are asked what change was supposed to be made and reply truthfully. Then your pants and underwear are removed and your dick is placed in a machine, it's too late now, the process has begun.
When the machine is removed you look at yourself in the mirror, you lost a bit of weight as a side effect, and you think you might look a bit more androgynous. But most importantly you look at your crotch and see nothing but pubic hair, no genitals at all. You look down to get a better look at your new crotch and start feeling it a bit. It feels so strange to have nothing down there, just smooth skin and a pee hole. It feels like you should still have a dick there, but there's just nothing...