HELP ME PLEASE I CANT COPE ANYMORE!!!?

every time i log into yahoo answers or youtube or anything else whenever i want to do anything like comment or whatever else i get logged out without my permission. it happens all the time and its just happened to me twice now on yahoo answers so ive had to type this question 3 times. and even when i ask to keep signed in for 2 weeks it still does it. im getting stressed wiv it now and its gettin pathetic what do i do??