It sounds like you were bordering on awareness within the dream, but weren't quite aware enough to make a conscious decision as to whether you were dreaming or not. That happens to me every once in a while. Work on awareness more, and be more skeptical of reality during the daytime. After all, dreams seem real when we're not lucid in them, and we accept things without question. They feel normal. But then again, waking life feels normal too, so what's the real difference?