I bought Fallout 3 for pc shortly after it came out. So the version I have doesn't have the new levels on it. Is there anyway to get the new levels without buying the game again?

To get the new levels you will have to purchase the Broken Steel add-on. It was bundled with Point Lookout when it was originally released on DVD, but you can buy Broken Steel by itself on Steam.

IIRC you can add mods that remove the level cap