What should I do?

Sydney
My boyfriend and I have been together for over 3 years. We are both 21. I am ready for marriage, have been for a while (a few years.) My boyfriend says he is no where near ready (maybe not even a few years from now). I try not to bring it up too much but it's just what I want soo badly. He says he feels bad for making me sad. 
I get mad whenever I see engagement photos or wedding photos of people my age or younger getting married or engaged because they have what I want so badly. If he isn't ready soon I don't think I can do it anymore. The last thing I want to do is break up with him because I love him sooo much but it just hurts my heart and I feel like a failure. I feel that way because these couples that are getting married who are younger than me or have barely been together both know what they want. And what they both know is that they want to be together forever. And I feel like I failed because I have been with someone for over 3 years and I can't get him to feel the same way. I want someone who knows what he wants and wants it at the same time as me. I have no idea what I should do. I don't think I can fully express how much I want marriage and how much it means to me and how much it hurts that I can't have it right now.
Obviously I'm not going to do something just because it got the most votes, I will do whatever I think is best. But I just want to know what other people's opinions are.
Sorry that this was long, I personally hate reading long posts so hopefully people actually read this haha.

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