My account doesn't exist.

Whenever I log into minecraft.net, it won't let me change my name or skin. Instead, it tells me to buy the game. I own the game, and if I refresh the page enough times, it lets me change my name. However, if I refresh it too fast, I get logged out, and it won't let me log back in saying (something similar) "OOPS! We could not validate your access, please try to login again."