Mojang Loading Screen

My minecraft wont launch properly, it launches, but gets stuck on the Mojang loading screen. it launched twice but crashed just a minute after it worked. I have tried everything from deleting it to changing the options. Please help me.
It worked completely fine, then suddenly crashed without me doing anything. I downloaded shaders the time I played, before it stopped working, but i've tried deleting everything I have of minecraft and mods on my computer but it won't work.