If a guy changes his smile and body language toward you, does that mean anything?

Okay guys, help me out. I have asked several female friends, and none of them can figure this guy out, though they all seem to think he is interested in some unconventional way. This guy in my class is so cute, and artsy, friendly, funny, and otherwise just normal. You'll just have to take my word for this, but I have always been the pretty girl, even though the past few years I've also been overweight. What attracted me initially was that-literally the second I walked into class on the first day-he saw me and kind of just stared for several seconds, but not in a weird way, more in a way that he didn't realize he was doing it. I might have imagined it, except that when he realized I didn't yet have my book, he offered to share his book with a deer-in-the-headlights kind of expression. As someone who had been overweight and had cute guys stop being interested in me for several years, it was really endearing. That being said, since that point, while I've lost 20 pounds ***for healthy reasons***, he also seemed to have lost interest in me. I tend to become colder and determinedly act uninterested when I like a guy, which is pretty much what I did for the first half of the semester, as well as flirting a teensy bit with another guy in the class. It's a really small class, and the idea was that he might become jealous when he heard about it; obviously, since then, my male friends have told me it was a stupid/manipulative idea, so I stopped doing it. Since then, because he loves music, I asked him if he would be willing to look at lyrics I wrote, and he told me to FB them to him. I did, and he didn't respond. At this point, I would have decided he was completely uninterested, but here's where it gets confusing. Since sending the lyrics, every time we have been in class, the first thing he does when he/I enter the room in the morning is look directly at me. Before class, I'll lean down to rummage through my bag, look up to ask him something, and he'll be leaning forward looking directly at me, as if waiting to start a conversation. Never once before I sent the lyrics has he started a conversation with me; since then, if there is ten minutes of conversation among classmates, he will probably start three conversations with me, pertaining to arbitrary questions from observances. He has mirrored my body language and looked at me as he's doing it...I even wasn't sure if he really was, so I pretended to be confused when I saw him mirroring a particularly unusual posture and immediately changed my posture, and he spent like five seconds shifting around trying to decide if he should change his posture or not. Not to mention the more typical signs, like him sitting with his legs open and pointed toward me, stretching his arms behind his head and then looking my way, etc. When I eventually just asked him if he ever looked at the lyrics, he said he did and they were really good, but he doesn't normally collaborate, so he doesn't know...and he likes to know the story behind lyrics before he works on them. My friends said it was a loaded question, that he wanted to know more about me, since they were interesting lyrics for sure, but wouldn't he have just replied on facebook that my lyrics were really good, he definitely wants to help me with them, and maybe I can tell him the story behind them? I am so confused. I would say he might just be boosting his ego by seeing if I'll openly respond to the subtlest indication that he's interested, but I don't think he's the type, and my friends also believe that he's definitely interested but that they don't exactly get it. And, yes, I know I could always just be more upfront with him, but I tried that in the beginning of the semester by saying something about his hair, and the other guys looked at him like there was an inside joke happening, so I am not brave enough to try it again.