Insecurity

I have a 1st time partner. it's been 3 years since I have met him.... I believe he is the love of my life and was made for me. but there is one major issue between us... which is him eyeing other female in front of me while we are out in public. This draws out so much insecurity, frustrations, resentment and other emotions toward him. I would call this a deal breaker. But then I go back to loving him so much. what can I do about this specific issue? I have brought it up 3 or 4 times already since 2016 and forgave him repeatedly, silently...