HI Mugz,
According to my humble experience, yawning helps you to maintain your body awake.
If you just keep yawning maybe you aren’t ready to sleep yet.
Have you tried exhaling hard at once first and then taking slow deep breaths?
Have you tried meditation?
Also, maybe you should try other techniques first instead of WILD.
We always like to recommend MILD, VILD and WBTB under these circumstances.
Recommended Long Read:
Big VILD topic.
MILD Tutorial
Big WBTB Topic
Short Read:
VILD is mostly about imagining the dream setting you would get lucid. Usually by creating a context you would RC.
MILD is about repeating phrases that you want to stick to your mind, so you would probably recall it during the dream, possibly to RC or to be motivated enough.
WBTB is about waking up and getting back to back. Some people fall asleep faster when getting back to bed in the middle of sleep, which helps you to get into a dream much easier than initial bedtime.
Also, the techniques are not 100% fool proof. You cannot expect them to work at first attempt, sorry, but it’s true. You should insist on them.
Good luck.