Is he interested and just shy, or is he just a friend who was busy?

I know it's not much to go on, but me and this guy have been friends for a while and I think we're both pretty shy. So anyway I feel like he's interested sometimes and other times I'm not so sure. It seems like he is though and others agree he is. As for me I feel like sometimes I'm being obvious then other times I feel like I'm too subtle, because everything I do could be interpreted as me just being friendly. It's really confusing. So I went out of my comfort zone here and asked to hang out.

So I sent him a fb message asking to hang out. I mentioned that I was asking this way because I didn't have his number and I felt like there was never a chance to ask in person. So I mentioned that we talk at school but never hang out and that we should, and suggested Sunday since I was free that day. However all he said was "I would like to, but I'm going to ____ on sunday.." Something like that, but I took out the place for security. It was out of town basically.

My question is, if they were interested and were busy wouldn't they ask for another time to hang out? Or be like here's my number, I'll text you when I'm free? But being just a friend he wouldn't suggest another time? All he said was he would like to but was busy. Is that an easy way to reject me? Be honest guys, because I'll seriously give up if he's just too nice to say flat out he doesn't like me. (And yes I realize I'm probably way over analyzing this.)