There are many kinds of dreamsigns, and I'm pretty sure everyone has at least one. It could be anything from being in some completely strange situation, to seeing things that can't possibly happen in RL. It's just a matter of finding it. Have you been keeping a dream journal? If you haven't I'd suggest it. It can help you figure out your sign. Also, don't be looking for the wrong thing. Dreamsigns aren't always some image that happens again and again in your dreams.