Login for Macbook Pro keeps popping up.

It's the keychain login, which is the same as my password to get into the computer, that keeps popping up when I'm working. I can't find any way to stop this. My desktop is still open and all my apps are too, documents, etc. But I can't move until I enter that password. It's not that I am using a new program that might need a login. It's been working for some time and is open.