how come my google isn't googling properly?

when i search for something on google, when i click on whatever comes up, at least 4 out of 5 times i get something entirely unrelated, like monster.com or dealtime or something totally not what i asked for or clicked on. then when i hit the back button it says page has expired. i don’t get these things when i use other search engines, but i like to use google. i am wondering if my google is corrupted or something, or why could this be happening? help!!