need help with a boy!!!?

There's this guy I've been really good friends with for about five years now. Friends, that's it. But then I noticed when I came home from university this summer he was friendlier than normal.. and I didn't really mind. He's been acting really flirty, he'd hug me every time he saw me, etc. Then one party he asked me to stay over but I had to go home, and since then we've been texting and such. He's super flirty over texts, and started saying stuff like "we should hang out" or when I'd say I was having a nap after work he'd say something like "I wish I was there too" So I was getting a little nervous just because it was a big change from our previous relationship. But we went camping this previous weekend with a bunch of people and we pretty much knew something was going to happen. Except it didn't. Miscommunications and stuff and we ended up spending each night separate. He seemed really weird around me too, barely talking, talking to my girlfriends more than me. I didn't really know how to take it. So I texted him yesterday and it totally wasn't like our usual conversations. Instead of me being the slightly timid one now it's him. He seemed so serious, not taking any jokes. Then randomly it'd seem like he was night, but then he'd go cold again. Now when I said we should hang out he's like "yaaa maybeee! but i work a lot and am usually pretty tired" Why is he doing this? I feel like it's completely flipped and I don't know what to do! Someone please help! Explain to me why he's acting so different, and is there anything I can do?!