Everytime i log in, the game crashes

The game will not start for me.
When i press the "play" button on the launcher, it should take me to the Minecraft main menu.
But instead, it got stuck on the Mojang loading screen. About 5 or so seconds later, my game crashes. Is it a system error? I just need some feed back because it has never done this before.

Steps to Trigger bug:
1. Start launcher
2. Click play
3. Wait 5 seconds while on the Mojang loading screen