Marriage

I'll start by saying I just turned 28 years old and my boyfriend will be 51 this June. We meet in July of 2017. Our relationship was only sexual at first. We became a couple in February of 2019. By this time we were already living together. He's been married twice. Both were 8-11 years. I myself have never been married. I've asked him about marriage and he's said he doesn't want to get married and divorced for third time. He's said he'll think about it. Am I wasting my time? Does he not wanna marry me because of me or is it really because he's been there done that like he's said? I haven't got to experience much of those sweet once in a lifetime moments like prom, graduation, childbirth etc. So marriage is a really big deal for me.