www.gires.org.uk
It all sounds reasonably common, tbh. As long as you stay calm, and discuss appropriately, you will be far more helpful than getting hysterical.
I do understand it's a hard thing to come to terms with, and you are entitled to your reactions, but in all honestly, you need to sit down and think this through properly. Your son is still the same person, whether ultimately he transitions or not. You are entitled to your feelings.
Shriveling and dramatising and wringing hands isn't going to make it any easier for him to open up to you, and he probably does need someone to talk through.
Is he registered with a clinic? Ask him which one. He can't be on the waitlist for surgery as he hasn't fulfilled all of the criteria.
Stop being histrionic, and start educating yourself, as much for your sake as his.
If you aren't prepared to respect his wishes, he would be better off elsewhere. You don't have to agree with his wishes, but you have to stop being hysterical and start listening. Really listening. Not half listening and getting him to chuck pills away that you know are easily replaced.
And yes, I have a son with ADD and aspergers. And many times we have wondered if eventually he will start to become more gender fluid. He's too young yet, but you've known about this for a year at least. Why are you reacting in this manner? Surely you have been discussing it with him over the last year?
And clearly you missed the 'I understand why trans commit suicide' thread last week. Largely because of reactions like yours. Grow up, and deal with it. You are going to make the situation worse.