Am I wrong to want to be engaged/married?

So me and my SO have been together for almost 6 years. He'll be 30 in a couple of months and I am 26. We have lived together for 3 years and have been through a lot together - he's practically my carer as I suffer with depression and anxiety.

From the start of our relationship we both spoke about wanting to get married and have kids some day, and even from a year or two into our relationship I have been open to getting engaged as I knew he was the one, but I also knew that it might take him longer to make that commitment. However, each year that goes by I feel like it's never going to happen. Last year I asked him to marry me, because I thought he might just be nervous to ask, and he didn't really reply. He just laughed it off and said 'I'm meant to do that bit' and that he 'has plans'. It's now been almost a year since that day. I brought it up again a couple of months ago and said how downhearted I'd been feeling about it, because I've felt ready for a long time and I thought he was. We had a heart to heart and he was very lovely about the whole thing, but didn't really answer any of my questions.

We are financially stable, have a decent home, we both have lovely supportive families who get on really well with each other, we own two dogs and a lizard together and are super honest with each other. Am I being unreasonable for wanting to get engaged, or even just to know what's up? Every time I see someone post on social media about getting engaged, married or having children, I find it really difficult to cope and I question whether he really does want to be with me. I now barely go on social media and avoid TV programmes about weddings. I even had to quit my job which was to write about wedding venues because it made me so depressed to research into venues I couldn't have myself.

I obviously don't want to marry someone who isn't ready to be married and I definitely don't want to force him into an engagement, which is why I'm leaving the ball in his court. However I can't help feeling unloved, unappreciated and like he can't commit to me. Please help!