MacBook Pro, 13''. When I restarted my computer, the screen didn't boot up. The grey apple appeared and the loading icon. What should I do?

I've already had this problem once, when I updated my computer. The grey apple appeared and the loading sign. So I turned the computer off, and turned it back on again pressing COMMAND-R. Then, once I was on Mac OS X Utilities I tried Reinstall Mac OS X, but I couldn't because it said Recovery HD and Macintosh HD were locked.

So then I tried Startup Disk, so that I could restart my computer and in the end that worked, because my profile picture came up and I could eventually put my password pin in.

The problem now is that it has happened again. I have tried the same system, but it isn't working this time. When I try Restart with Startup Disk, it either doesn't boot up as before, or my profile picture appears, I put my password pin in and it doesn't let me log in. It comes back to the same profile picture. The password is correct, because it doesn't shake, but the screen seems to go back to the login-profile picture.

What should I do?