He still has been doing it but I haven’t been saying anything just hurt feelings. what should I do?

So I am currently working on losing weight but my boyfriend dated all skinny girls before me and when we’re in public he stares at all skinny pretty girls and though I have told him how it makes me feel he gets upset and calls me insecure.
He still has been doing it but I haven’t been saying anything just hurt feelings. what should I do?
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