I think I've had lucid dreams before, without actually trying... Is this possible?

One example, that usually happends alot, is whenever I have nightmares, I can become aware that I'm dreaming, and force myself to wake up from the dream. If things get violent or way to scary, I either try super hard to control what happens, or force myself to wake up.

Also, I researched this whole website and the forum, and I havn't really read anything about people having sexual lucid dreams. I have once or twice, where I can control what happens. I'm not going to get into details.. But hasn't anyone else experienced this?