Hey, and welcome to Lucid Dreaming!

If you are having troubles with your nightmares, i'd suggest looking over this tutorial: http://www.dreamviews.com/community/...ead.php?t=5309. I highly doubt that this could be effecting your Lucid Dreaming attempts THAT much, but you never know.

And you said something about you know when your dreaming, but all you see is black. Here, you are more than likely not dreaming. Your brain produces images while you are sleeping. These look like "real life" and sometimes can even seem MORE clearer then in real life. So like I said, if you are dreaming and you know your dreaming then you will have some kind of imagery or sensation.