Why do guys say " go talk to your side niggas" in a relationship?

Well I don't know. like ig me & my boyfriend argue for no reason & he always says " go talk to your side niggas" which I don't have? & I told him that & he still doesn't bealive me? & he either says "okay " or " stop lying" & then sometimes he says " bye" to me & when I was mad I said "bye " then he put crying faces saying "no ! :( " but this Is my question why do some guys say that in a relationship?
Why do guys say " go talk to your side niggas" in a relationship?
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