My boyfriend has very little self-esteem...help?

My boyfriend and I have been dating for about 6 months now. When we first started dating, he was infatuated with me, and wrote lovely things on my Facebook wall and when I was with him he told me he felt wonderful and carefree. Over the past month and a half or so, I've noticed that he hasn't been as sweet or so attentive of me. This made me upset, but I can see why. He has a lot of stressors right now. He just bought an apartment to move into when he goes back to school, which is 2 hours away from where I live. He is worried about moving in and being able to still see me. The biggest issue though is that he never feels he is good enough. It's not really things with our relationship, but more things in the outside world. He started posting poetry on Tumblr, which I thought was a good idea to get his words out there, but instead he just thinks that all the things he writes aren't good, when really they are. I've told him time and time again that I really wish he saw in himself what I see in him. Plus, I want my old boyfriend back. Do you think it's his stressors that are causing the change, or his self esteem issues? How can I help boost his self esteem?