I need some help asap!?

well ok i know hacking is bad but is there a way i can get into my bf's facebook. i feel he's flirting with some other girls or cheating on me,i always ask him if he does it and he says no he would never do that but i just want to make sure. i tried everything from downloading and stuff like that i just want something where i can download it for free with no spams or making you fill out a survey in order to continue or if i can do it without downloading things even better and free even better. if anyone can help me please i will appriciate it so much!! :)