Congrats on lucid dreams!
Don't be discouraged, sometimes getting next lucid dream takes time, but you will definitely get them more often if you continue practicing and keep the right mindset.
And yeah, as BrandonBoss said sounds like WBTB is a good technique for you, and length will definitely improve even more, get your goals ready for when you get your first decent length one.

*Moved to Lucid Experiences*