You told yourself you would be lucid after opening the door, but didn’t know it was a dream before that? Dream logic, gotta love it. 
‘Waking up’ into another dream is called a False Awakening. There’s some info here if you’d like to read about them. =]
Yes, you’re getting closer to a lucid dream. 
Like Basilus said, RCs can get you places. You might want to try a little autosuggestion as well. 
Hope this helps, feel free to ask any more questions. ^^
