Why doesn't he want to be exclusive/serious?

So I've been seeing this guy for about a month. We hang out at least once or twice a week. for hours. He pays for everything. We use to date in high school for like three months. Then we went are separate ways, that was three years ago. I always felt like he was the one that got away. Well he added me on facebook and then we started talking again every night. Then we started calling and hanging out again. Well last night I told him I've been thinking about him and he said I've been thinking about you too. I asked him what he thought about me he said he liked me a lot and I was a lot of fun to hang out with, but he didn't want to get serious. I told him I could respect that, which is true. But then he went on saying it was because we were going to two separate colleges and they're rival schools. However, when he was saying it his voice pitch changed and he was kinda stuttering. Also he'd come home to his parents' place and I would too every weekend. So that really didn't make sense. I'm a psychology and criminal justice major, that works at a law firm. I have a really good bull sh*t detector. Also we haven't had sex, even though we've had plenty of opportunities, the time we got pretty close to doing it he was shaking like he was nervous so we didn't. Also the way he smiles at me and looks at me I know he's genuine. So what could it be? Is he scared? He broke up with me the first time, so it's not I'll walk out of his life again. From what little I've told you, you can tell he's a bit of a pansy, but what other reasons could it be or sounds like?