HELP ME!!!!!!! ITS REALY URGENT!!!!!! PLEASE!

I login to my wp-admin and then i click on settings and t again ask me to login! Everytime i perform any task, it asks me to login! Like if i login to wordpress admin panel then i will go to dashboard and then if i click on add new post then it will again ask me to login! I mean everytime if asks to login! Even if i click on remember me! I changed the theme but its still there!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!