Should I stay with him or leave?

My boyfriend and I have been together for 4 years and have been living together for almost 2 years. I am 18 and he is 21. I know it seems we’re too young but our families love each other and we get along great. We are also both college students. I have been having dreams about marrying him and am very happy with our relationship right now. Sadly, he refuses to open up to me about marriage. I understand that he is 21 years old and that we are both not ready for marriage but you would think that since I’ve been with him for 4 years he would potentially see me as his wife in the future, but no. He shuts marriage out of his life and it really hurts me. It makes me feel like I’m not good enough to be seen as his wife and all he said was that his main priority right now is school and getting a good job when he graduates. I feel like he is not committed to me anymore and just don’t understand what’s so wrong about thinking about marriage with me. I’m not asking him to propose right now or anything. I don’t even want to get married until 10 years from now but I always think about our future together. I see him as a great husband and father so why can’t he see me as a great wife and mother? I don’t want to pressure him but I feel trapped and don’t want to waste my time on someone that isn’t looking into the future with me. I don’t want to be with him for 15 years and still not be married. and he has talked about marriage and even promise rings with one of his ex girlfriends so why can’t he do the same with me? am I not good enough? I am so confused and just need some advice. So here is the main question: should I break it off or just suck it up and stay with him? Thanks.