Right, I am going to be honest with you here.
Both the sentence structure and grammar of your post seem to suggest that you do not like to read or write. Are you educated? Did you study at university? Your boyfriend is finishing a very language intensive and precise degree. Are you able to keep up with him?
Is his level of education very different from yours? Are you able to discuss things on his level? What kind of career do you have? What sort of prospects do you have?
What I am trying to say is that if you are very different from him, he may not feel like you are a very good fit. If, for instance, you are reading Cosmo in bed and trying to talk to him about manicures, and he is reading about inchoate offences in preparation for moot court and is trying to talk to you about mens rea, you may not have a lot in common - certainly less than you did seven years ago when you were sixteen.
This is not to say that it couldn't work. My niece who works in retail, and who has no qualifications at all, is married to an electrical engineer and they seem happy enough. However, they have only been married a couple of years and I don't know if it will work long term. They only got married because she became pregnant, which is not an option I would recommend.
Most of the time, if there is a vast difference in education levels, it is the same type of issue as a large difference in religion, or social class, or wealth, or politics. It can work out but it is difficult.
If this is the case, he may be thinking that you don't have enough in common to be married for the rest of your lives. It is something you need to speak to him about. And this is a valid problem.