Should I give this guy a chance?

We've been seeing each other on and off since August. I really like him, and he made it clear he likes me, too -- even if we've had few dates, there's lots of calls, messages, etc. However, the past two weeks he's been pretty distant.

I sent him a FB message (we haven't added each other), and he didn't answer. I texted him last Friday and the same. Later on, he texted back and apologized, saying it was because of finals and he'd been sick, but I had more finals than him, so I can't accept that as an excuse.

I called him earlier, and he didn't take the call, just texted me that he'd call tonight (and he almost always does call if he says he will).

I seriously like him, but I'm starting to doubt him, and the last thing I want is to be the girl who can't take a hint and keeps being pushy. But, I also know he's insecure and I'm afraid if I back off too much he'll just give up on me.

I don't know what to do. Should I give him one more chance, or just give up already?