Scard to get married

I have been with my fiancé for 4 almost 5 years in March. He is all for getting married we have two kids and have lived with each other for 1 and half years. But I feel like once people get married they always get divorced.... No doubt I want to spend the rest of my life with him. But I asked why we need rings and a  piece of paper to prove our love and he got mad... Idk