Confused love?

So im engaged to the love of my life been together over 2 years, I always think to myself I could never love anyone else like this and get anxiety thinking of being with anyone else. But my fiancé he has done some mean thing to me in the past such as pushing, name calling, not defending me, missing important events, flirting with girls (but God knows I'm not a saint) and dont get me wrong he has his moments where he acts amazing! But me and my fiancé broke up before and I saw other people and didn't like it. He promised he'd change but he still throws fits and acts weird, Everytime I think of leaving again my anxiety comes back.. idk if i should stay after all I've been through or if i should move on..

Advise??? Please im only 18 and very confused