#1. It's not overuse ... you've only done 200 miles.
#2. You DESPERATELY need to get your bicycle professionally fitted. Urgently. Right now. Your butt hurts, your knees hurt, and your ankle hurts ... this is absolutely NOT normal. Cyclists can ride a 1200 km randonnee (that's 750 miles in 3.5 days) and not be in as much pain as you are right now.
#3. You NEED to see a Dr. right now. I'm not a Dr. but I have torn my Achilles tendons, and it sounds like that could be what you've done. If it is, you could be off your bicycle for the next 6 months ... all because you didn't set your bicycle up correctly.
#4. You are aware you can change your saddle, right?
First thing in the morning, go and see a Dr. When you get out from seeing the Dr, contact the Oregon Randonneurs:
http://www.orrandonneurs.org/ to see who they would recommend as a bicycle fitter in your area.