It very well could be your monitor. When I am color correcting video I plug in an old-school CRT monitor (broadcast not computer) or a TV to see how things look 'in reality'.
If you don't have access to a monitor or the correct connections to plug one it. I would suggest burning off a few minutes to DVD and looking at that on a regular TV/DVD player to see if, in fact, it is as dark as you think.
-jay