There is many, many ways of achiving lucidity. What you are describing is probably the MILD technique. (Memonic induced lucid dream) Try using different techniques, such as:
WILD (Wake induced lucid dream) etc.
Or you could keeping a dream journal for a week and look for special "Dream signs" (Signs that prove the fact that you are dreaming) Then remember your "dream sign" and eventually you will se the "dream sign" in a dream thus making you lucid.
Or you could buy the "Lucid dream" dose for your I-doser. Although i haven't tried it yet, it probably increases the odds of you becoming lucid.
These are just a fraction of all the avalible techniques to lucid dreaming! Keep trying! Hope this helps!