Why is my best guy friend (who I'm secretly in love with) pushing me away?

I've been good friends with this guy for nearly a year now, and in the last 4 months we've become inseparable. We'd spend as much time together as possible, he'd cancel plans with other people to see me (including his girlfriend, which I know is terrible) and we genuinely just got along fantastically. Then it started getting weird. I can't pinpoint exactly when it happened, but the last few times we've hung out, the atmosphere has been different. He's not as forward as he was and doesn't joke as much, he doesn't seem as totally comfortable with me, the other day he told me I looked nice and then quickly changed the subject before I could respond, and he's started making physical contact - he rested his arm on mine in the cinema, put his hand on my waist to steady me when I was walking around a gate, held onto the sleeve of my jacket while walking down his driveway etc. This is strange in itself; him and I have always had very strong boundaries since he has a girlfriend, and seriously didn't ever touch at all. To make this even more confusing, it's like he's started to push me away; he doesn't text me as much as he did, when before he'd text at least once a day just to see what's up. I thought maybe he's sick of me or something, but when I contact him, he never seems like I'm bugging him, he texts back straight away and seems to be more than happy that I texted him. He listens to everything that comes out of my mouth, asks me about things going on in my life and remembers what I say, and instead of greeting me at the door in his pajamas if it's 10pm and we're just gonna watch movies, he's fully dressed and has done his hair. He's started to never let me pay for anything, but he says no and makes excuses when I ask if he wants to hang out, and then will ask me if I want to do something like it was his idea; controlling or what?! He's just started university, so he has a lot less free time than he did before, but it still seems to me that he just isn't as keen to have me around all the time as he was before.

To make this even more complicated, I think I've developed feelings for him over the past few months. I haven't told him or done anything even close to letting him know, so I'm fairly certain his new behavior isn't due to awkward feelings or anything; if anything, I act like I don't care. The fact I feel this way about him, though, means I'm constantly overanalyzing every darn thing he does and says or doesn't say or do, and I'm at a complete loss right now for why he's acting this way. Is he truly just busy, and should I just back off and wait for him to realise he misses me (if he does) and contact me? Should I continue making an effort to see him even though he always says no unless he comes up with the plans? Am I blowing this all way out of proportion and should just sit down and relax? Is he just simply tired of me as a person? Or (and I'm trying to stay away from this possibility because I really hate false hope) has he developed similar feelings for me and isn't sure how to proceed? Seriously, any insight or help at all would be so appreciated; I am going out of my mind! Thanks!
Why is my best guy friend (who I'm secretly in love with) pushing me away?
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