Getting frustrated can often cause problems with lucid dreaming. Dry Spells are going to happen and the best way to get out of a dry spell is by forgetting completely that you are having one. Try to act as if you have been lucid every night this month and expect to get lucid again once you fall asleep. I don't think you are doing anything wrong at all as far as your practice is concerned. I just think you are stressing too much. Just try to relax and fall asleep knowing, 100%, that you are going to lucid dream. If you don't, then simply act as if you did and do the same thing the next night. Keep your mind positive and keep up your technique practices. Make sure you are having fun with it and not trying too hard.