Not Ready

Ok girls I really need your advice and opinions on this and it will probably be a long story so bare with me. I'm 21, my boyfriend is 20 but will be turning 21 in a few months. We've been together for 2 years and are juniors in college. We've lived together as "roommates" at an apartment on our campus for 6 months now. When we first got together I never took the relationship seriously and thought it would end once we transferred to other universities once we got our associates degrees, but he said he wanted to follow me because he saw a future with me. He used to say all the time about how he wanted to propose at our sophomore graduation and I used to tell him he was crazy because I thought he was joking, but he would always say he was being serious. I told him I wanted to wait to get married, until a few months later when something bad happened in my life and he was there for me and I realized I really could see myself marrying him. So I told him that I was all in, that I wanted to marry him. I thought he would be happy because he talked about it so often but instead he seemed taken aback and next thing I know he's saying "there's no rush, I won't be proposing to you over the summer but you will definitely get a ring within the next two years at our follow on university. We're three months away from our senior year and now it's "well let's wait until after I come back from BOLC and ranger school." (we're both in the military and now we're talking at least a year after we graduate). And everywhere around me I just see people getting engaged left and right and getting married and having kids and it's not even that I want to get married right away, I still want a few years before my wedding but I just want to be with someone who wants to be with me in the future and knows they want to marry me. I would love to have a really long engagement, I already have a ring from my mom so it's not an issue of him not having money for a ring. Tonight hit me hard because I saw my ex roommate who was the spawn of Satan just got engaged to a man she knew for a year and it was a LDR. And I just kept thinking "someone wants to be with that with for the rest of their life. I'm a halfway decent person in a serious relationship and no one wants to commit to me but someone wants to marry her." And I started crying. So my boyfriend asked me what's wrong and I told him I didn't want to talk about it because the only thing worse than having someone not be sure about marrying you after being with you for years and living with you for half a year is then making that person feel forced and pressured into proposing to you. But he pleaded with me to tell him so I did. We ended up fighting over it. I told him it just hurt to be with someone for so long (and be of legal age it's not like we're 15) and them not know if they want to commit to being with you in the future and he said "I want to be with you for now." And I just felt my entire heart crumble. He realized how it sounded and tried to reword it but he kept going on saying he's only 20 and he's young and guys his age don't want to settle down yet. But I just don't get it because he IS in a serious relationship. We practically are married without all the paperwork, we live together and have intertwined al aspects of our life. And I told him it sucked because i consider myself to be invested in this relationship meanwhile he stepped into it but is leaving the door open behind him. He said the for stays open until there's a ring on my finger and I pointed out that that was exactly my problem because it just feels like instead of working through issues he just has the excuse to turn around and leave. And now he's saying he doesn't want to get married until he's 27 and I completely understand personally now being ready for marriage but I just figured that when you meet the person who you truly love, you wouldn't have to wait 9 years to realize they're the one. I love and adore him and he treats me like gold, I'm willing to wait but I don't want to be with someone who feels so iffy about me. Need some words or reassurance here or some relatable stories. I just feel so sad and my hormonal cycle isn't helping.