Why can't I log in to Minecraft? unknown username or password

My Minecraft password will not work. I've reset it about 5 times and no matter what I choose as my password, it will not take it. I just made my Minecraft account today

I am entering my username correctly, and I am typing everything in the correct boxes, but it always says "Unknown username or password...". I know I am putting my username in correctly because if I try to re-register, it will not let me use my email because it's currently in use.

Could somebody explain to my why no matter what my Minecraft password is, it won't work?

If your account is actually a Mojang account, which I believe all new accounts are, you should actually be using the email address you signed up with in the username box.

Counter intuitive I know, but they still haven't changed it from when you actually used your username.

If you are already using your email address to log in

The login servers may be down. Always check help.mojang.com when you have login problems!