serious talk during sex

My guy started talking about marriage soon after we started dating. I always said he was crazy, he would say that I was going to marry him someday, so I said I have 2 yrs left of school then we can talk. After that he stopped talking about it. Today during sex he asked me if he bought me a ring, would I wear it?? I absolutely love this man and I know he adores me, but really, why say that in the middle of sex??? Is he serious