Hm...have your tried these? :
1) Re - running Minecraft
2) Force Updating Minecraft
3) Deleting the .minecraft folder
4) Restarting your computer
5) Restarting your modem / router
6) Restarting...your...LIFE
![Tongue :P](https://www.opticraft.net/Smileys/flat_emoji/tongue.gif)
Also, perhaps try going on at a later time?