Advice To Regain His Interest?

In the beginning of the relationship, he chased me hard, and I made him work for it a little. He wrote poems for me, played guitar and sang for me, and he always wanted to talk and asked to do so before I could. We live 45 minutes away, but he made time to see me. Less than a month later, he is already not being romantic, he doesn’t text or call unless I do it first, and he cancelled our Valentine’s day plans to study for a test that he knew about for over a week, so he said he was sorry and promised he’d make it up to me, but he hasn’t even brought up rescheduling our plans yet. I know that saying “you should do this or that” doesn’t work, so I have avoided that, so I try encouraging him like “you know how you used to send good morning texts? That made me so happy and meant a lot to me” and it worked, he started sending good morning texts again and he was enthusiastic :D however, he doesn’t want to open up emotionally anymore, and when I have a bad day he just says “oh” and he doesn’t seem to enjoy our texting conversations anymore. He seems normal and happy to be with me when we Skype, but getting him to Skype is almost impossible now, and so I asked him about it gently, and he said sorry and that he promised we would Skype the next night, but the night he promised, he fell asleep before we could Skype… I have to say I am a good girlfriend, I am low maintenance, but he knows I don’t put up with crap, I am always enthusiastic about seeing him and talking to him, but I give him his space and even tell him that I’m glad he doesn’t text me when he’s with his friends. I do not act needy (at least I try), and when he’s having a hard time I comfort him (even though he doesn’t comfort me…) and I tell him that I appreciate him when he does something for me… what am I doing wrong? I really want this to work out but it seems like he is losing interest! I really need advice before I make more mistakes and ruin our chances of getting past this obstacle. Thank you so much!
-Selena