Within login history, you're able to view failed and successful error attempts:

Errorneous attempts

Errorneous attempts will show you failed attempts. The reason of failure will be indicated as well. For example, a correct e-mail address but a wrong password.

Recent sessions

The recent sessions listing will show you succesful login attempts. This can be used to see if it is really you who has been logging in.

If you see a session that isn't you, you can terminate that session and log out other users from a distance.