Why would a guy do this?

After about a year of dating this guy (on and off) I finally told him I love him and he said he wasnt ready to say it back. He came over the same night though and he held me and we watched TV and he kept kissing me and he treated me great. Over the past couple of months things have been really great. He would show PDA and we would always hang out when we werent working. He would make me dinner, always make sure I didnt need anything. He was always affectionate and just great to me. I told him I had to leave for new mexico, I live in AZ, for about 6 months for school and I asked him to wait for me and not see other people while I am gone and I would be back in AZ 1 time a month over the 6 months. He said he didnt want to do that, that he had needs and he was human too. I told him I would do it for him because I love him and he said "sorry I am not going to say that back." Is this a clic case of fear of commitment or is there more to this that I am not seeing