I'm at the end and expected it to be like Fallout 3 but instead the game just finishes :brokencomputer:

Why did you expect it to be like Broken Steel? Where did you hear it had any relation to it? :sadvaultboy:

You must play it before the battle of Hoover Dam. Wander around and you'll get the quest.

So if you don't have any saves pre hoover damn you're screwed?

Pretty much.
Have to start a new character.

Don't complain about it though.
If you failed to research the DLC before purchase then the developers are not to blame.
Just remember that.

Actually they would be because of a failure to warn somebody :shakehead:

No, they're not.
You failed to do the research on your own and just blatantly expected that it was gonna be like Broken Steel.
No one is to blame but yourself.

They don't have to "warn" people about anything.
If the DLC allowed post final quest gameplay then it would have stated so in it's description.
It did not.