I'm guessing you brought up the guy's age, because he's 20something, young, and might be flighty. Age difference is usually something that can be overcome, but in this case? It looks like the gap is too much. I'm sure he likes you, but most people tend to develop the more serious relationships with people their own age.
You need to be more like a guy is, in these cases. Enjoy the eye candy for what is is, but don't get too attached, Men wouldn't. You needn't, either.