Someone keeps going into my boyfriend's facebook?

[Hannah]

Someone keeps going into my boyfriend's facebook account and liking all these adult themed and pornographic pages on Facebook and I know my boyfriend doesn't read FHM magazine and doesn't watch porn but he keeps making a new facebook and someone knows his password.What should we do? he doesn't know how to unlike a page. The pages are upsetting me.
my password is alot stronger than his I just pick a word i like and translate it into a foreign language and I add four numbers at the end. He is not doing this
someone liked a dating website link on an app called speeddate.com over a week before my birthday in 2011 and these people are causing alot of trouble.