Boyfriend troubles

Alright so,
For the past 7 months my boyfriend has been adding girls that he doesn't know on fb.. And I keep telling him it bothers me but he doesn't seem to care.. He won't even delete them and just keeps telling me 'it's facebook'
Please don't hate on this. 
I just need to know what I should do, every time I approach it he gets shitty.. 

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