Marriage

I have been with my SO for almost 4 years. Together we have 3 girls. My daughter, his daughter, and our daughter. He is 9 years older than me and has been married once before. He claims his marriage was so horrible that it has traumatized him from all marriage. He says he loves me and wants to be together forever but refuses to marry me. I have always believed in marriage and have expressed its importance to me. I can't help but envy his past relationship. Sometimes I feel so bitter about the fact he married her but won't offer me the same chance. I try to get over it but just can not...😩