Too big of an age gap?

So I've been dating this guy for a little more than a month now and we really hit it off. We see each other almost every day and just enjoy being together. We've even spent a few nights together. But our age gap (I'm 18, he's 25) seems to be an issue.

Whenever things start to get hot, I try to *ahem* make a move on him, and he basically dodges. He'll finger me, but essentially avoid my touch.

When I asked him about it, he just said "It's obvious that you're young. I guess old dudes should be into that."

The age gap doesn't seem to bother him enough to avoid me all together, but it also blocks any physical intimacy. I feel like a child.

Is there any way to make him more comfortable? What should I do?