Why do females do this?

any bloke I am with they will do their best to get his attention away from me.I am a female model and ppl say I look nice,but this is destroying my life,.any man I date is bombarded by offers from other women,then being a man he will get tempted,and wen he tries to come back to me I tell him to piss off,I am getting bitter,they are allowed to flirt with my man,and there own guy hjas to sit there looking at his feet,he can't even look up wen i am there.what is this about?????