Laptop screen won't work. Login is bugged?

So all of a sudden I restart my computer and I go to the login screen of my laptop, where you put your password. I login in, and after 5 seconds it goes back to the login screen again. It just sends me back there instead of starting. It gives me a black flash and then sends me back to it no matter how many times I try to login. I tried safe mode, but obv couldn't login. -_- I tried to repair but didn't work. Anyone know what else I can do? :|