What to do for me and my boyfriends 3 year anniversary?

The obvious idea is to go out to eat and see a movie but we do that a lot, and I want it to be different, special, and romantic. I'm 18 and he's 20 so we can't go camping or do something like that. And I don't have much money, and I don't even know what to get him! Or if im supposed to help pay for what we do that day. (for the other anniversaries we just ate and went shopping and saw a movie). I don't know what to do!