Have you tried doing any reality checks? I've found them quite helpful lately. Just last night, I did a reality check using clocks (the time on the clock on wall didn't match the time on my watch, and I became lucid).

Usually, you'll need to establish some dreamsigns so you can recognize certain aspects of your dream as actually being a dream - pair that with a reality check and it may help you cross the threshold into lucidity. This is where your dream journal comes in handy - it's easy to recognize patterns and dreamsigns when you have them written out in front of you.

Everyone's different, so you'll just have to try different things and find what works best for you. Good luck!