Feel like I’m losing interest in the idea of marriage

I’ve been with my SO for a couple years now and marriage has always been a common topic in the relationship he was previously married (I was not) and I would love to get married one day. But honestly it just feels like we are never going to get married even our kids we have one together and share 3 kiddos who we have full custody of ask him all the time why he hasn’t asked mommy to marry him yet. Whenever we talk about it he just says “getting engaged adds too much stress to a relationship” or “our relationship is too rocky to get married now” he also constantly jokes when someone asks if he’s gonna be someone that waits 10 years he says “woah let’s not rush it”. Idk am I wrong? I used to be so excited to get married and be able to call him my husband and I honestly just feel like it’s never going to happen.